Neuroscience 2011 - Presentations from Winnipeg scientists

Abstracts are below the schedule.

  Session Start Time
Presentation Time
Location 		Pres #
& Type		 Poster Board # Authors & Institutions Abstract Title
Session # & Title
Sat 11/12 1:00 PM
3:00 PM - 4:00 PM

Hall A-C 		46.07
Poster 		M6 *Y. DAI1, E. DENERIS2, L. JORDAN1; 1Univ. Manitoba, Winnipeg, MB, Canada; 2Dept. Neurosci., Case Western Reserve Univ., Cleveland, OH Cholinergic modulation of serotonergic neurons in the brainstem of ePet-EYFP mice

46.Modulation of Neuronal Firing Properties I
Sat 11/12 1:00 PM
1:00 PM - 2:00 PM

Hall A-C 		59.21
Poster 		DD30 R. M. ZACHARIAH, C. OLSON, V. R. LIYANAGE, *M. RASTEGAR; Biochem. and Med. Genet., Univ. of Manitoba, Winnipeg, MB, Canada Understanding the pathophysiology of rett syndrome towards developing novel therapeutic strategies.

59.Rett Syndrome
Sun 11/13 1:00 PM
3:00 PM - 4:00 PM

Hall A-C 		262.11
Poster 		DD24 *H. AUJLA, C. O'DUNN; Psychology, Univ. of Winnipeg, Winnipeg, MB, Canada The effects of chronic exposure to stress and alcohol on alcohol-based conditioned place preference

262.Alcohol Drinking, Preference and Reward II
Sun 11/13 1:00 PM
3:00 PM - 4:00 PM

Hall A-C 		289.11
Poster 		UU14 *M. SABRI1, C. HUMPHRIES1, J. MANGALATHU1, E. LIEBENTHAL1,2; 1Neurol, Med. Col. of Wisconsin, MILWAUKEE, WI; 2Univ. of Manitoba, Winnipeg, MB, Canada Effects of memory load on the processing of task-irrelevant speech sounds

289.Imagery and Modeling
Sun 11/13 1:00 PM
2:00 PM - 3:00 PM

Hall A-C 		302.10
Poster 		XX22 B. ROGALA1, *Y. LI1, X. CHEN1, S. LI1, G. J. KIROUAC1,2; 1Oral Biol., 2Psychiatry, Univ. of Manitoba, Winnipeg, MB, Canada Effects of inactivation of kappa opioid receptors with norBNI on sensitized fear following a single episode of footshock in rats

302.Molecular Influences on Fear and Anxiety
Mon 11/14 8:00 AM
9:00 AM - 10:00 AM

Hall A-C 		402.06
Poster 		XX89 *M. MCHUGO1, S. DUKIC2, R. PIECH4, S. SMITH5, B. ABOU-KHALIL3, D. ZALD2; 2Psychology, 1Vanderbilt Univ., NASHVILLE, TN; 3Neurol., Vanderbilt Univ., Nashville, TN; 4Inst. of Neurosci., Trinity Col., Dublin, Ireland; 5Psychology, Univ. of Winnipeg, Winnipeg, MB, Canada Emotionally enhanced attention is preserved in patients with unilateral amygdala damage

402.Emotion: Disorders and Dysfunctions
Mon 11/14 8:00 AM
11:00 AM - 12:00 PM

Hall A-C 		408.04
Poster 		ZZ27 *S. LI1, G. KIROUAC2; 1Oral Biol., 2Oral Biol. and Psychiatry, Univ. of Manitoba, Winnipeg, MB, Canada Comparative study of the source of inputs to the anterior and posterior aspect of the paraventricular nucleus of the midline thalamus

408.Prefrontal and Striatal Anatomy and Function
Mon 11/14 1:00 PM
1:00 PM - 2:00 PM

Hall A-C 		516.01
Poster 		YY90 X. CHEN1, Y. LI1, S. LI1, *G. J. KIROUAC1,2; 1Dept Oral Biol., 2Psychiatry, Univ. of Manitoba, Winnipeg, MB, Canada The effect of exposure to novel or shock context on the activation of orexin neuron in a rat model of shock-induced fear sensitization

516.Animal Models of PTSD
Mon 11/14 1:00 PM
2:00 PM - 3:00 PM

Hall A-C 		516.02
Poster 		YY91 *X. CHEN1, Y. LI1, S. LI1, H. BERGEN2, G. J. KIROUAC3; 1Oral Biol., 2Human Anat. and Cell Biol., 3Oral Biol. and Psychiatry, Univ. of Manitoba, Winnipeg, MB, Canada Elevated prepro-orexin mRNA expression in a rat model of post-traumatic stress disorder

516.Animal Models of PTSD
Tue 11/15 1:00 PM
3:00 PM - 4:00 PM

Hall A-C 		676.03
Poster 		AA23 *A. KAMBOJ1, P. LU1, M. B. COSSOY2, J. L. LEMAISTRE1, G. DE MURCIA3, C. M. ANDERSON1; 1Div. of Neurodegenerative Disorders, St Boniface Hosp. Res. Ctr., Winnipeg, MB, Canada; 2Dept. of Intrnl. Med. (Neurology), Univ. of Manitoba, Winnipeg, MB, Canada; 3Ecole Supérieure de Biotechnologie de Strasbourg, Illkirch Cedex, France Poly(ADP-ribose) polymerase-2 deletion reduces neuroinflammation and demyelination in experimental allergic encephalomyelitis

676.Neuroinflammation Mechanisms
Tue 11/15 1:00 PM
1:00 PM - 2:00 PM

Hall A-C 		705.13
Poster 		TT15 *U. SLAWINSKA1, H. MAJCZYNSKI1, L. M. JORDAN2; 1Nencki Inst. of Exptl. Biol., Warsaw, Poland; 2Physiol., Univ. of Manitoba, Winnipeg, MB, Canada The upright posture facilitates plantar stepping in spinal rats through processes requiring afferents from the plantar surface of the foot

705.Spinal Cord Injury: Training and Locomotion-Animals
Tue 11/15 1:00 PM
2:00 PM - 3:00 PM

Hall A-C 		705.14
Poster 		TT16 *L. M. JORDAN1, Y. DAI1, M. LEOPOLDO2, E. LACIVITA2, K. MIAZGA3, H. MAJCZYńSKI3, A. M. CABAJ4, U. SLAWINSKA3; 1Dept Physiol., Univ. Manitoba, Winnipeg, MB, Canada; 2Dept. Farmaco-Chimico, Univ. degli Studi di Bari "A. Moro", Bari, Italy; 3Dept. of Neurophysiol., Nencki Inst. of Exptl. Biol. PAS, Warsaw, Poland; 4Dept. of Bionics, Inst. of Biocybernetics and Biomed. Engin. PAS, Warsaw, Poland 5-HT2 and 5-HT7 receptor agonists facilitate plantar stepping in chronic spinal rats through actions on different populations of spinal neurons

705.Spinal Cord Injury: Training and Locomotion-Animals
Tue 11/15 1:00 PM
4:00 PM - 5:00 PM

Hall A-C 		705.24
Poster 		TT26 *K. C. COWLEY1, B. J. MACNEIL2, J. W. CHOPEK1, E. ZAPOROZHETS3, B. J. SCHMIDT4; 1Physiol., 2Physical Therapy and Rehabil., Univ. Manitoba, Winnipeg, MB, Canada; 3Physiol., 4Physiology, Intrnl. Med., Univ. of Manitoba, Winnipeg, MB, Canada Neurochemical excitation of thoracic propriospinal neurons improves hindlimb stepping in adult rats with staggered contralateral hemisections

705.Spinal Cord Injury: Training and Locomotion-Animals
Tue 11/15 1:00 PM
4:00 PM - 5:00 PM

Hall A-C 		708.08
Poster 		VV1 *C. W. MACDONELL, K. E. POWER, J. W. CHOPEK, K. R. GARDINER, P. F. GARDINER; Spinal Cord Res. Centre, Dept. of Physiology, Fac. of Med., Univ. of Manitoba, Winnipeg, MB, Canada Modulation of rat motoneuron properties leading up to, and immediately following fictive locomotion

708.Motor Neurons: Development, Identification, Intrinsic Properties, and Modulation
Tue 11/15 1:00 PM
3:00 PM - 4:00 PM

Hall A-C 		708.11
Poster 		VV4 *J. W. CHOPEK, C. W. MACDONELL, K. E. POWER, K. GARDINER, P. F. GARDINER; Spinal Cord Res. Centre, Physiol., Univ. of Manitoba, Winnipeg, MB, Canada Variation in quipazine enhancement of flexor and extensor monosynaptic reflexes includes presynaptic and motoneuronal mechanisms

708.Motor Neurons: Development, Identification, Intrinsic Properties, and Modulation
Tue 11/15 1:00 PM
4:00 PM - 5:00 PM

Hall A-C 		722.16
Poster 		XX68 *K. VADAKKAN; Univ. of Manitoba, Winnipeg, MB, Canada Semblions induced through inter-postsynaptic functional LINKs, biological parallels of K-lines, as basic units of internal sensations

722.Action, Sensation, and Perception
Wed 11/16 8:00 AM
9:00 AM - 10:00 AM

Hall A-C 		766.22
Poster 		E2 *E. E. VASQUEZ-DOMINGUEZ, W. BAUTISTA, B. FEDIRCHUK; Physiol., Univ. of Manitoba, Winnipeg, MB, Canada Acetylcholine induces a hyperpolarization of voltage threshold in neonatal rat spinal motoneurons

766.Modulation of Neuronal Firing Properties II
Wed 11/16 8:00 AM
10:00 AM - 11:00 AM

Hall A-C 		775.27
Poster 		U2 *L. CONANT1, E. LIEBENTHAL1,2, A. DESAI1, J. BINDER1; 1Neurol., Med. Col. of Wisconsin, Milwaukee, WI; 2Physiol., Univ. of Manitoba, Winnepeg, MB, Canada Phonemic perception in children with developmental dyslexia: An fMRI study

775.ADHD, SLI, Dyslexia, and Other Specific Disorders of Neurobehavior II
Wed 11/16 1:00 PM
1:00 PM - 2:00 PM

Hall A-C 		868.01
Poster 		D7 *S. CURTI1, G. HOGE2, F. DAVOINE3, J. I. NAGY4, A. E. PEREDA2; 1Physiol., Sch. of Med., Montevideo, Uruguay; 2Dominick P. Purpura Dept. of Neurosci., Albert Einstein Col. of Med., Bronx, NY; 3Inst. de Ingenieria Electrica, Facultad de Ingenieria, Montevideo, Uruguay; 4Physiol., Univ. of Manitoba, Fac. of Med., Winnipeg, MB, Canada Properties of electrical synapses between Mesencephalic Trigeminal (MesV) neurons

868.Synaptic Transmission: Electric Synapses and Gap Junctions
Wed 11/16 1:00 PM
2:00 PM - 3:00 PM

Hall A-C 		919.06
Poster 		TT14 *S. N. MARKIN1, A. N. KLISHKO2, N. A. SHEVTSOVA1, M. A. LEMAY1, B. I. PRILUTSKY2, D. A. MCCREA3, I. A. RYBAK1; 1Dept. Neurobio. and Anat., Drexel Univ. Col. of Med., PHILADELPHIA, PA; 2Sch. of Applied Physiol., Georgia Inst. of Technol., Atlanta, GA; 3Dept. Physiol., Univ. of Manitoba, Winnipeg, MB, Canada Neuromechanical model of spinal control of locomotion

919.Motor Pattern Generation: Models
Sun 11/13 6:45 PM
6:45 PM - 7:45 PM

156 		SAT057
Satellite / Ancillary Events 		Satellite Organizer: *K. VADAKKAN; Div. Neurology, Univ. of Manitoba, Winnipeg, MB, Canada Semblance Hypothesis of Memory: Computational Modelling and Development of Artificial Circuits


ABSTRACTS

46.07/M6. Cholinergic modulation of serotonergic neurons in the brainstem of ePet-EYFP mice
*Y. DAI1, E. DENERIS2, L. JORDAN1;
1Univ. Manitoba, Winnipeg, MB, Canada; 2Dept. Neurosci., Case Western Reserve Univ., Cleveland, OH
It has been shown previously that 5-HT neurons located in the
parapyramidal region (PPR) of the medulla play a role in generating locomotion.
Electrical or chemical stimulation within the 5-HT neurons of the PPR produces
locomotion in the isolated neonatal rat brainstem-spinal cord preparation. Injections
of a cholinergic agonist into the PPR in adult rats elicit locomotion, and
electrical stimulation in the PPR elicits locomotion in adult rats. Locomotor
activity in adult rats and mice gives rise to c-fos expression in these PPR
neurons, showing that they are normally active during voluntary locomotion. Using
ePet-EYFP mice in which EYFP was expressed in 5-HT neurons of the brainstem, we
showed that the PPR neurons received an excitatory cholinergic input and could
be classified into three categories (single spike, phasic firing and tonic
firing). In this study we further investigate the modulation of 5-HT neurons
through activation of cholinergic receptors of these neurons. Using the same ePet-EYFP
mouse model we performed whole cell patch-clamp recordings on EYFP+
neurons of the brainstem (PND 7 - PND 15). 5-HT neurons of the brainstem demonstrated
location-related responses to acetylcholine (ACh). Similar to our previous
report, bath application of 15-20 µM ACh generally produced sustained
depolarization of the membrane potential (6.7±3 mV, n=6), hyperpolarization of
voltage threshold (-2.0±1 mV), lowering of rheobase (-7.8±8 pA, -37%) and
reduction of input resistance (-297.8±377 MΩ, -48%) in the PPR 5-HT neurons. Some of these neurons also displayed membrane
oscillations or transferred from type 1 (single spike) to type 2 (phasic) or type
3 (tonic) neurons when ACh was administered. In contrast to 5-HT neurons in the
PPR, however, 5-HT neurons located in the midline raphe nuclei of the brainstem
had a reduced or no response to ACh. No substantial change was found in membrane
potential (0.7±2 mV) and voltage threshold (0.9±3 mV) in many of these neurons
in the presence of 15-20 µM ACh. However, a small increase in rheobase (6.0±12
pA; 28%) and a decrease in input resistance (-269.2±179 MΩ, -18%) were still
observed. Hyperpolarization of the membrane potential by ACh was also shown in
a few 5-HT neurons in the PPR, and a few cells of the midline raphe nuclei displayed
depolarization of the membrane potential resulting from ACh application. The
different responses to ACh produced in neurons of the PPR and the midline raphe
nuclei of the brainstem suggest that neurons in these two areas may play
different functional roles, with the PPR neurons the major contributors to the initiation
and control of locomotion.



59.21/DD30. Understanding the pathophysiology of rett syndrome towards developing novel therapeutic strategies.
R. M. ZACHARIAH, C. OLSON, V. R. LIYANAGE, *M. RASTEGAR;
Biochem. and Med. Genet., Univ. of Manitoba, Winnipeg, MB, Canada
Rett Syndrome (RTT) is a neurological disorder and the best-known form of Autism Spectrum Disorders (ASD). ASD refer to neurological diseases, compromising the communication and socialization behaviors of 1 in 150 individuals by age 3. RTT is the primary cause of cognitive disability in females resulting from mutations in the Methyl CpG Binding Protein 2 (MECP2) gene (MECP2: human gene; Mecp2: murine gene; MeCP2: human/murine protein). Currently, Rett Syndrome has no effective treatment. However, in RTT mouse models, re-activation of the Mecp2 gene after the onset of disease have been shown to rescue the RTT symptoms. This raises hope towards RTT therapy prospects either by delivering MECP2 into the affected neurons, or through drug treatments targeted towards protein candidates, both of which may compensate for MeCP2 loss in neurons. We hypothesize that specific point mutations compromising MeCP2 activities, will result in impaired neuronal function and aim to understand the involved pathophysiological mechanisms. With advanced neuroscience and cutting edge gene therapy techniques, we are studying fundamental unanswered questions on molecular functions of MeCP2 in neurons and aim to shed some light into the pathophysiological mechanism of Rett Syndrome. Our results will lead to therapeutic strategies for Rett Syndrome and autism that currently have no effective treatment. This work is supported by funds from the Manitoba Institute of Child Health (MICH) and Children’s Hospital Foundation of Manitoba, Manitoba Health Research Council (MHRC), Scottish Rite Charitable Foundation of Canada (SRCF), Natural Sciences and Engineering Research Council of Canada (NSERC Discovery Grant 372405-2009), University Research Grants Program (URGP) and Canada Foundation for Innovation- Leaders Opportunity Fund (CFI-LOF).



262.11/DD24. The effects of chronic exposure to stress and alcohol on alcohol-based conditioned place preference
*H. AUJLA, C. O'DUNN;
Psychology, Univ. of Winnipeg, Winnipeg, MB, Canada
Exposure to stress or ethanol has been shown to dysregulate systems related to reward and anxiety-like behaviour. While previous studies have typically focused on the acute effects of stress, drug relapse often occurs during protracted withdrawal - a period not characterized by overt physical symptoms. The present study was designed to address the impact of a alcohol experience, exposure to chronic stress or a combination of both on alcohol-seeking behaviour. Thus, male Wistar rats were subjected to either a 6-week chronic unpredictable stress regimen, ethanol liquid diet, both concurrently, or neither. Following two-weeks, subjects were tested on the elevated plus maze, a pharmacologically validated model of rodent anxiety, and for ethanol-conditioned place preference (CPP) (0.25, 0.50, or 1.0 g/kg). Results replicate and extend previous findings that revealed alterations in the acquisition of alcohol seeking, by demonstrating dose-response changes in ethanol CPP resulting from stress and ethanol history.



289.11/UU14. Effects of memory load on the processing of task-irrelevant speech sounds
*M. SABRI1, C. HUMPHRIES1, J. MANGALATHU1, E. LIEBENTHAL1,2;
1Neurol, Med. Col. of Wisconsin, MILWAUKEE, WI; 2Univ. of Manitoba, Winnipeg, MB, Canada
The fate of task-irrelevant information is still at the heart of ongoing theoretical debate. According to the Load model of attention (Lavie, 2005, 2010), the load level (high, low) and the type of processing (perceptual, cognitive control) imposed by a task, determine the extent to which irrelevant information is processed. We recently demonstrated a linear relationship between perceptual load and blood-oxygen-level-dependent (BOLD) response to task-irrelevant speech sounds in auditory temporal regions implicated in syllable processing. The lowest perceptual load was associated with the strongest activation in syllable processing regions, and the highest load with the weakest activation. Here, in order to test the predictions of the Load model with regard to cognitive control, we compared simultaneous event-related potentials (ERP) and functional magnetic resonance imaging (fMRI) recordings associated with ignored speech at high and low working memory loads. Twenty participants performed an N-back task in one ear (Attend ear) while ignoring task-irrelevant speech sounds in the other ear (Ignore ear). In two blocked experimental conditions, memory load was either low (1-back) or high (2-back). Accordingly, accuracy was best in the 1-back (93%) and worst in the 2-back (85%) memory load condition. The 1-back compared to the 2-back load was associated with a lower mean BOLD response in speech-related areas, in the left middle and posterior superior temporal gyrus (STG) and sulcus (STS), and the right middle STG. Similarly, the N2 ERP component (150-200 ms) following irrelevant-syllables was smaller in amplitude across frontal and central electrodes in the 1-back compared to the 2-back condition. The weaker speech-related BOLD response in the left STG-STS and right STG in the 1-back compared to the 2-back condition is consistent with the Load model, whereby lower working memory load is predicted to minimize distractor processing due to higher availability of cognitive control resources responsible for maintaining current task priorities. The lower N2 amplitude in the 1-back load may reflect the weaker attentional and executive demands related to the processing of the syllables in that condition.



302.10/XX22. Effects of inactivation of kappa opioid receptors with norBNI on sensitized fear following a single episode of footshock in rats
B. ROGALA1, *Y. LI1, X. CHEN1, S. LI1, G. J. KIROUAC1,2;
1Oral Biol., 2Psychiatry, Univ. of Manitoba, Winnipeg, MB, Canada
Exposure of rats to an acute episode of footshock leads to an enduring behavioral state, which involves sensitized fear responses (immobility) to novel environment and noises. Other research has shown that the expression of an acute negative emotional state (depressive- and anxiety-like behaviors) produced by a single episode of stress is mediated by the endogenous opioid peptide dynorphin and the kappa opioid receptor (KOR). The purpose of the present study was to determine if inactivation of KORs by giving the KOR antagonist norbinaltorphimine (norBNI; 15.0 mg/kg, s.c.) before (48 hrs) or after (48 hrs) footshock exposure (5 × 2 s of 1.5 mA over 3 min) attenuated the expression of the sensitized fear responses to novelty in rats. At Day 9, shocked and nonshocked rats were placed in a novel chamber (L22 cm × W28 cm × H35 cm) for 7 min. The novel chamber exposure consisted of a quiet period (first 3 min), presence of a novel 5 kHz 90 dB noise (3 min) and another quiet period (1 min). At Day 10, rats were placed in the shock chamber for 5 min. For both tests, behavioral activity was videotaped for subsequent analysis and ultrasonic vocalizations (USVs) were recorded. The amount of time the rats spent immobile (freezing) and the number of rearing episodes were scored and USVs analyzed for the presence of frequencies in the dysphoric range (20-30 kHz). We reported that exposure of rats to acute footshock produced lasting and enhanced immobility in shocked rats when placed in a novel or the shock chamber. However, pre-shock or post-shock norBNI administrations had no effect on the amount of immobility or rearing expressed in shocked rats placed in a novel chamber or the shock chamber. Also norBNI had no effect on the number of dysphoric USVs emitted by shocked rats placed in either the novel or shock chamber when compared with the saline group. Time dependent microstructural analysis of ethological behaviors (immobility, rearing, and grooming) expressed when rats were placed in the chambers is ongoing and the results will be presented at the meeting.



402.06/XX89. Emotionally enhanced attention is preserved in patients with unilateral amygdala damage
*M. MCHUGO1, S. DUKIC2, R. PIECH4, S. SMITH5, B. ABOU-KHALIL3, D. ZALD2;
2Psychology, 1Vanderbilt Univ., NASHVILLE, TN; 3Neurol., Vanderbilt Univ., Nashville, TN; 4Inst. of Neurosci., Trinity Col., Dublin, Ireland; 5Psychology, Univ. of Winnipeg, Winnipeg, MB, Canada
Emotionally salient events are presumed to attract attention through an amygdala-dependent neural system. Anderson and Phelps (2001) showed that patients with bilateral or left amygdala damage fail to exhibit emotion-facilitated stimulus identification during an attentional blink task. A recent study failed to replicate this finding in two individuals with bilateral amygdala lesions (Bach et al. 2011). Lesion etiology and age of onset are critical differences between these studies (anteromedial temporal lobe resections in adulthood vs. Urbach-Wiethe disease, a congenital disorder). We sought to replicate the Anderson & Phelps procedure in a sample of adult patients with unilateral medial temporal lobe resections that included the amygdala. Patients with left (n=3) or right (n=4) MTL resections and demographically matched healthy adults (n=7) participated in the study. Participants viewed 224 trials of a RSVP stream of 15 words (150msec/item) and were asked to report the identity of two green target words among black distractor words. The first target word (T1) was always neutral whereas the second target (T2) could be an arousing/taboo or neutral word (matched to arousing T2 for length). T2 words appeared in positions (lags) 1-7 of the RSVP stream following T1. For all analyses we measured T2 report accuracy conditioned on accurate T1 report (T2|T1 accuracy), collapsed into early (1-3) and late (5-7) lags following the procedure in Anderson and Phelps (2001).
We conducted a mixed effects ANOVA on T2|T1 accuracy with the factors Lag (early, late), T2Emotion (neutral, arousing) and Group (healthy, left lesion, right lesion). We found a main effect of Lag (F(1, 11)=14.73, p<0.05), a main effect of Group (F(2,11)=6.66, p<0.05) and a T2Emotion*Group interaction (F(2,11)=5.83, p<0.05). In order to further examine the interaction, we conducted follow-up analyses of the influence of T2 emotion on T2|T1 accuracy within the different groups. There was a trend for better identification of arousing compared to neutral T2 in the healthy control group (F(1,11)=3.99, p=0.071). Contrary to the findings reported by Anderson and Phelps, we found significantly better T2 accuracy for arousing compared to neutral T2 in the left lesion group (F(1,11)=7.62, p<0.05) but not in the right lesion group (F(1,11)=3.10, p=0.11). These data suggest that the amygdala is not a critical mediator of the emotional modulation of attention.



408.04/ZZ27. Comparative study of the source of inputs to the anterior and posterior aspect of the paraventricular nucleus of the midline thalamus
*S. LI1, G. KIROUAC2;
1Oral Biol., 2Oral Biol. and Psychiatry, Univ. of Manitoba, Winnipeg, MB, Canada
The paraventricular nucleus of the thalamus (PVT) is part of a group of midline and intralaminar thalamic nuclei implicated in arousal and stress. While previous anatomical and functional studies have emphasized the importance of the brainstem and hypothalamus as the main source of afferent inputs to the PVT, none of the studies have examined the comparative density of neurons from the different regions of the brain that project to the PVT. Consequently, this study examined the source and density of all brain afferents to the PVT using the placement of iontophorectic injections of the retrograde tracer cholera toxin B (CTb) restricted in the anterior (aPVT; n = 4) or posterior (pPVT; n = 4) PVT in the rat. Sections (50 µm) of the brain were immunoreacted for CTb using diaminobenzidine (DAB) as the histochemical marker. A semi-quantitative approach was taken in which CTb-labeled neurons from the different nuclei that innervated the PVT were counted on every 5th sections. We found that the major source of inputs to the PVT was from areas of the medial prefrontal, insular cortex and ventral subiculum of the hippocampus. The largest number of retrogradely labeled neurons was found in the prelimbic and insular cortices following injections in the pPVT. Other areas of the brain including the infralimbic, periaqueductal gray, and parabrachial nucleus and dorsomedial nucleus of the hypothalamus contained a moderate number of retrogradely labeled neurons. In contrast, the number of retrogradely labeled neurons following injections of CTb in the aPVT was found to be the greatest in the subiculum and the prelimbic cortex. The infralimbic cortex, insular cortex, periaqueductal gray, parabrachial and dorsomedial nucleus of the hypothalamus contained fewer retrogradely labeled neurons following injections in the aPVT. The results of the present tracing study clearly show that many more neurons in the cortex project to the PVT than neurons from areas of the hypothalamus and brainstem. Besides inputs from the parabrachial and periaqueductal gray, no other significant brainstem input to the PVT was detected in this study. This is of interest because previous studies on the PVT have emphasized a brainstem influence on PVT functions. However, the comparatively larger number of cortical neurons retrogradely labeled from the PVT in the present study indicates the importance of limbic cortical inputs on the PVT.



516.01/YY90. The effect of exposure to novel or shock context on the activation of orexin neuron in a rat model of shock-induced fear sensitization
X. CHEN1, Y. LI1, S. LI1, *G. J. KIROUAC1,2;
1Dept Oral Biol., 2Psychiatry, Univ. of Manitoba, Winnipeg, MB, Canada
Orexins are arousal peptides produced exclusively in neurons in the hypothalamus. In this study, we wanted to determine if orexin neurons were activated when shocked rats are placed in the shock context (associative fear) or in novel chambers (non-associative fear). Rats (n = 27) were exposed to footshocks (5 x 2 s episodes of 1.5 mA randomly given over 3 min) whereas control rats (n = 28) were placed in the chamber but no shocks were given. As we previously reported, shocked rats displayed immobility and avoidance to novel chambers, noises, and conspecific rats at both early (Days 9-12) and later (Days 24-31) time points. At approximately 5 weeks after initial footshock exposure, the number of orexin neurons expressing Fos was assessed in rats taken from their home cages or following a 15 min exposure to a novel chamber (clear plastic cylinder measuring 28 cm in diameter) or the shock chamber. For these experiments, subgroups of rats with homogenous fear sensitization were produced by assigning individual subjects into each group (home cage, novel and context chamber) based on their immobility response to novelty, which was measured one day after footshock exposure. Behavioral activity was videotaped and subsequently analyzed for immobility and rearing expression. Two hours after exposure to either novel or shock chamber, rats were anaesthetized and perfused with 4% ice-cold paraformaldehyde. Their brains were removed and sectioned for immunohistochemical double labelling of orexin neurons and Fos proteins. Double labelled neurons were quantified for both the lateral and medial population of orexin neurons. The behavioral results showed that shocked rats displayed higher level of freezing and less rearing in the novel chamber and shock chamber compared to the nonshocked rats. Nonshocked and shocked rats placed in the home cage showed very little behavioral activity. The immunohistochemical results indicated that no differences in the percentage of orexin neurons expressing Fos were detected between shocked and nonshocked groups exposed to the different chambers. In contrast, the percentage of orexin neurons expressing Fos was increased in the medial orexin group in shocked and nonshocked rats exposed to the novel and shock chambers when compared to rats placed in home cage. These results indicate that orexin neurons are activated when rats are placed in a different environment than their home cage but that this activation is not related to reactivation of the fear memory nor the fear sensitized state expressed by shocked rats.



516.02/YY91. Elevated prepro-orexin mRNA expression in a rat model of post-traumatic stress disorder
*X. CHEN1, Y. LI1, S. LI1, H. BERGEN2, G. J. KIROUAC3;
1Oral Biol., 2Human Anat. and Cell Biol., 3Oral Biol. and Psychiatry, Univ. of Manitoba, Winnipeg, MB, Canada
Post-traumatic stress disorder (PTSD) is a psychiatric disorder that can develop when individuals experience a stressful and life-threatening event. Orexins (hyprocretins) are peptides that have received a large amount of attention for their role in behavioral arousal. Since PTSD is a condition involving hyperarousal (hypervigilence, fear sensitization, and anxiety), we wanted to determine if orexin synthesis was increased in a rat model of PTSD. Single housed rats (n = 8) received a single session of electrical footshock (5 x 2 seconds episodes of 1.5 mA over 3 minutes) while control rats (n = 6) were exposed to the shock chamber but did not receive shocks. Shocked rats displayed a fear sensitized state (increase immobility to novel chambers and noises) that lasted for 4 weeks post-shock. Rats were anaesthetized 31 days after the shock exposure and were transcardially perfused with ice-cold PBS. The brains were removed, quickly frozen and sections of the hypothalamus were made (20 µm). The brain sections were then processed for in situ hybridization with an oligonucleotide probe for prepro-orexin mRNA. The brain sections along with 14C microscale were exposed to film for 10 days. The optical density of the area where orexin neurons are found along with 14C microscale standard strips was measured and analyzed with Image-J to quantify the expression of prepro-orexin mRNA. Results show that the orexin gene expression in the hypothalamus was increased in shocked rats. More specifically, prepro-orexin mRNA was found to be significantly higher (F(1,12) = 11.543, p < 0.005) in the medial part of the orexin population of shocked rats (332.4 + 33.6 nCi/g) when compared to nonshocked rats (191.9 + 15.2 nCi/g). More importantly, the prepro-orexin mRNA expression in the medial portion of the orexin population was found to be correlated with the amount of immobility expressed in the novel box with no noise present (r2 = 0.658, p < 0.001) or the presence of noise (r2 = 0.5497, p < 0.002) tested on Day 30 post-shock. In addition, prepro-orexin mRNA expression was also correlated with immobility in the shock context (r2 = 0.6499, p < 0.001) tested on Day 23 post-shock. The results indicate that the orexin system may be functionally upregulated in a rat model of PTSD and that this upregulation is correlated with both associative and non-associative fear expression. These findings are of interest because orexins are arousal peptides and hyperarousal is a key symptom of PTSD.



676.03/AA23. Poly(ADP-ribose) polymerase-2 deletion reduces neuroinflammation and demyelination in experimental allergic encephalomyelitis
*A. KAMBOJ1, P. LU1, M. B. COSSOY2, J. L. LEMAISTRE1, G. DE MURCIA3, C. M. ANDERSON1;
1Div. of Neurodegenerative Disorders, St Boniface Hosp. Res. Ctr., Winnipeg, MB, Canada; 2Dept. of Intrnl. Med. (Neurology), Univ. of Manitoba, Winnipeg, MB, Canada; 3Ecole Supérieure de Biotechnologie de Strasbourg, Illkirch Cedex, France
Experimental allergic encephalomyelitis (EAE) is an animal model of multiple sclerosis that produces an anti-myelin immune response, blood-CNS barrier permeability, demyelination and neurological signs of disease. Previous studies have revealed that inhibition of Poly(ADP-ribose) polymerases (PARPs) protects against EAE. While this protection has largely been ascribed to inhibition of the PARP-1 isoform, we and others have determined that deletion of PARP-1 is not protective and may potentiate EAE neuroinflammation and outcomes. The current study examines the role of PARP-2 deletion in EAE. EAE was induced in age-matched PARP-2-/- mice and respective wildtype littermate controls, and neurological function was assessed daily using a detailed 14-point score system. Blood-spine barrier permeability was assessed by measuring central extravasation of intraperitoneal Na-fluoroscein (NaF). Spinal cord sections were stained with haematoxylin/eosin (H&E) to detect central aggregation of inflammatory cells, and solochrome cyanin to detect demyelination. Neuroinflammation was also assessed by staining for activated T-cell infiltration (CD4+) and migrating macrophage/microglia (CD11b+). Genetic deletion of PARP-2 significantly reduced the total disease burden over 60 days, peak neurological score, and significantly delayed the time to onset of neurological signs of disease. Ratios of spinal:serum NaF was markedly increased in wildtype EAE mice compared to the vehicle treated group (10-fold increase, p < 0.001). In contrast, EAE-induced blood-spine barrier permeability was roughly 75% reduced in PARP-2-/- mice, compared to wildtype (p < 0.001), indicating that barrier breakdown is largely dependent on PARP-2 activity. Significantly increased immune cell infiltrates were detected in H&E-stained spinal cord sections of EAE control mice (p < 0.001 compared to sham), while PARP-2 deletion reduced inflammatory infiltrates compared to wildtype EAE mice (p < 0.01). Similarly, we observed extensive demyelination in spinal cord sections of wildtype EAE mice but not in PARP-2-/- EAE mice. Finally, CD4+ T-cell and macrophage/microglial (CD11b+) infiltrates were significantly reduced by PARP-2 deletion. This study demonstrates the first description of a significant role for PARP-2 in EAE and have important implications for the design of neuroprotective strategies.



705.13/TT15. The upright posture facilitates plantar stepping in spinal rats through processes requiring afferents from the plantar surface of the foot
*U. SLAWINSKA1, H. MAJCZYNSKI1, L. M. JORDAN2;
1Nencki Inst. of Exptl. Biol., Warsaw, Poland; 2Physiol., Univ. of Manitoba, Winnipeg, MB, Canada
We previously demonstrated that simply placing spinal rats in the upright posture dramatically improves their locomotor capability. This improvement consists of proper placement of the foot on its plantar surface during well-coordinated weight-supported stepping. We refer to this form of locomotion in the spinal preparation as “plantar stepping”. Here we test the hypothesis that the appearance of plantar stepping in chronic spinal rats when they are placed in the upright posture requires activity in afferents that supply the spinal cord with information about loading of the hindlimb. The two possible sources of load information from the hindlimb are from cutaneous afferents in the foot pads on the plantar surface of the foot, and from the “load” receptors in muscles, including Golgi tendon organs and muscle spindles. We manipulated foot afferent feedback using local anesthesia with lidocaine injections (s.c. 2 x 0.5ml 2%) into the pads on the plantar surface of the foot bilaterally. Locomotor capability was evaluated with behavioral observations and EMG recordings of flexor (Tibialis Anterior) and extensor (Soleus) muscles of both hindlimbs during movements induced by tail pinching. Plantar stepping was tested in rats held in both the horizontal and the upright posture. These experiments were performed 3-5 months after spinal cord total transection at the thoracic level (T9) in adult rats. Inter- and intra-limb coordination was evaluated using polar plots of the relationships between the onsets of activity in pairs of muscles. Our results show that chronic spinal rats in the upright posture could be easily induced to engage in bipedal plantar walking without any specific intervention other than tail stimulation, while it was much more difficult to obtain any plantar walking in the same animal when its body was kept in the normal horizontal position. Foot anesthesia dramatically affected hindlimb plantar walking on the treadmill of rats in the upright posture. The effects were characterized by significant shortening of extensor burst activity and alteration of inter- and intralimb coordination. In rats kept in the horizontal posture foot anesthesia produced only a slight alteration in hindlimb movements. Air stepping, another means of removing the effects of feedback from load receptors, removed the capacity for plantar stepping and resulted in the loss of well-coordinated movement. The patterns of muscle activity observed during air-stepping were unaffected by foot anesthesia. We conclude that foot afferent input to the spinal cord is required for plantar stepping.



705.14/TT16. 5-HT2 and 5-HT7 receptor agonists facilitate plantar stepping in chronic spinal rats through actions on different populations of spinal neurons
*L. M. JORDAN1, Y. DAI1, M. LEOPOLDO2, E. LACIVITA2, K. MIAZGA3, H. MAJCZYńSKI3, A. M. CABAJ4, U. SLAWINSKA3;
1Dept Physiol., Univ. Manitoba, Winnipeg, MB, Canada; 2Dept. Farmaco-Chimico, Univ. degli Studi di Bari "A. Moro", Bari, Italy; 3Dept. of Neurophysiol., Nencki Inst. of Exptl. Biol. PAS, Warsaw, Poland; 4Dept. of Bionics, Inst. of Biocybernetics and Biomed. Engin. PAS, Warsaw, Poland
The descending serotonergic system plays a prominent role in the activation of spinal cord neurons involved in the production of locomotion. Both 5-HT2 and 5-HT7 receptors have been implicated in this effect. 5-HT2 and 5-HT7 receptor agonists are now being used widely to facilitate recovery of locomotion after spinal cord injury in pre-clinical trials. The specific neural targets for these drugs are unknown, however. Here we examine the effects of agonists of these two receptor types on locomotion in rats with chronic spinal cord injury. We placed the rats over a treadmill in either a horizontal or an upright posture, and elicited locomotor-like movement with exteroceptive stimulation (tail pinch).We used i.p. quipazine (0.3-0.5 mg/kg) to activate 5-HT2 receptors and 8-OH-DPAT (0.2-0.4 mg/kg) or LP-211 (20 mg/kg) to activate 5-HT7 receptors. Our results confirm that agonists for both receptor types are effective in activation of the CPG for locomotion and for improving inter- and intra-limb coordination. Full expression of plantar stepping still required input from exteroceptors when the animals were in the horizontal posture, however. The activation of 5-HT2 receptors was more effective in the production of the normal pattern of extensor motoneuron output during spinal stepping. In the absence of 5-HT2 receptor activation, the extensor bursts were too brief to provide for weight support throughout the stance phase. In the presence of quipazine, extensor activity was prolonged and plantar stepping was improved when the animals were in the horizontal posture. In the upright posture, quipazine had a detrimental effect on both intra- and inter-limb coordination. Activation of 5-HT7 receptors had a more profound effect on inter-limb coordination, reducing the incidence of left-right co-activation in the horizontal posture. It did not alter upright plantar stepping. Results induced by 8-OH-DPAT or LP-211 were similar, suggesting 5-HT1A receptor activation is not required for the actions of these agonists on locomotion. Combined use of quipazine and 8-OH-DPAT at a lower dose (0.1 mg/kg) had an additive effect, mitigating the need for exteroceptive stimulation to facilitate the activation of the CPG for locomotion, and resulting in plantar stepping with normal placement of the foot on the plantar surface, normal inter- and intra-limb coordination, and weight support. Activation of both receptor types was necessary for the full expression of the capacity for the CPG to produce plantar stepping in spinal animals. These findings indicate that neurons forming different components of the spinal system for locomotion are controlled by the different receptors.



705.24/TT26. Neurochemical excitation of thoracic propriospinal neurons improves hindlimb stepping in adult rats with staggered contralateral hemisections
*K. C. COWLEY1, B. J. MACNEIL2, J. W. CHOPEK1, E. ZAPOROZHETS3, B. J. SCHMIDT4;
1Physiol., 2Physical Therapy and Rehabil., Univ. Manitoba, Winnipeg, MB, Canada; 3Physiol., 4Physiology, Intrnl. Med., Univ. of Manitoba, Winnipeg, MB, Canada
We recently showed that a propriospinal relay system could transmit the descending locomotor command signal in the in vitro neonatal rat (Zaporozhets et al., 2006, J Physiol 572: 443). Further, hindlimb stepping can be elicited by electrical stimulation of the brainstem in approximately 30% of preparations in which all direct descending bulbospinal connections are lesioned (Cowley et al., 2008, J Physiol 586:1623). In addition, in preparations that did not step after staggered contralateral hemisections, hindlimb stepping could be facilitated by application of sub-threshold concentrations of various neurotransmitters to the thoracic spinal cord (Zaporozhets et al., J Neurophysiol ePUB March 30, 2011).
In order to test if these findings are relevant in the adult, we sectioned the left hemi thoracic cord (T2, T3 or T4) and the right hemicord at T9 in 27 adult female Sprague Dawley rats. Intrathecal catheters were implanted midway between the two hemisections (confirmed post-perfusion).
Over a 10-week recovery period, all animals showed some degree of spontaneous recovery, ranging from weak flexion-extension movements of the limbs without body weight support of the pelvic region, to body support and plantar surface stepping. Although hindlimb ataxia and/or weakness prevented independent locomotion without assistance for balance, two animals with histologically verified complete hemisections were able to perform hindlimb stepping with weight support and make appropriate plantar surface contact during treadmill walking.
The ability of acute intrathecal drug delivery to facilitate hindlimb stepping on a motorized treadmill was assessed at 3-week intervals. The following drugs facilitated hindlimb stepping (as assessed using video-kinematic analysis): serotonin (5HT) with N-methyl-D-aspartate; 5HT with di-hydrokainic acid; the 5HT agonist quipazine; and the 5HT agonist 8-hydroxy-di-n-propylamino-tetralin (8-OHDPAT). The alpha-noradrenergic agonist clonidine impaired hindlimb stepping. Based on dye injection prior to termination, the 7.5 - 15 µL injection volumes used in these experiments did not spread beyond the inter-lesion zone.
These findings show that limited spontaneous recovery of hindlimb stepping can occur in adult animals with simultaneously created staggered hemisections, and that drug application to thoracic spinal cord can facilitate hindlimb treadmill stepping in adult rats in the absence of direct bulbospinal descending input. The findings suggest that neurochemical facilitation of thoracic propriospinal neurons should be further investigated as a means of restoring stepping after human spinal cord injury.



708.08/VV1. Modulation of rat motoneuron properties leading up to, and immediately following fictive locomotion
*C. W. MACDONELL, K. E. POWER, J. W. CHOPEK, K. R. GARDINER, P. F. GARDINER;
Spinal Cord Res. Centre, Dept. of Physiology, Fac. of Med., Univ. of Manitoba, Winnipeg, MB, Canada
Previous reports suggest that hind-limb motoneurons become more excitable in decerebrate animals during fictive locomotion (FL) evoked via electrical stimulation of the mesencephalic locomotor region. Although indications of increased excitability have been cited, much less attention has been placed on the period immediately preceding and following FL. The purpose of this research was to examine whether changes in motoneuron active and passive biophysical properties coincided with the transition from rest to locomotion, and immediately following locomotion. The analyzed data considered the states of quiescence (sQ), the period prior to alternating ENG activity but during tonic increases in ENG amplitude (sT), fictive locomotion state (sFL), and up to two minutes after FL state (sA). Intracellular recordings from antidromically-identified flexor and extensor MNs in the L3-L4 region of paralyzed decerebrated Sprague-Dawley rats were collected with the use of glass microelectrodes. Instantaneous MN discharge during ramp current injection (5 s up, 5 s down) was plotted against current amplitude to calculate the slope of the linear F/I relationship, while the average membrane voltage change in response to a short (20-ms) 3-nA hyperpolarizing current was used to calculate IR. In addition, voltage threshold and rheobase (50-ms depolarizing pulse) measures were collected. Both active and passive motoneuron properties were altered. The F-I relationship shifted up and to the left and discharged at rates 2-to-3 fold greater during sFL compared to sQ and sA; this occurred despite a decreased slope (mean 46% lower sFL). Furthermore, the F-I relation during sA was shifted to the right compared to sQ, indicating a decrease in excitability. Modulation of voltage threshold began during the sT period, reaching an average hyperpolarization of 3.4 mV during sFL. Interestingly, during sA the Vth reached a level more depolarized than that at the sQ phase in the majority of cells. Input resistance did not change systematically among states, while rheobase decreased during sT and further during sFL. The average decline in rheobase was 20%, attained during sFL. The data suggest that modulation of motoneuron excitability begins during the tonic state immediately preceding FL, and continues throughout locomotion. Perhaps most surprising is the relative decrease in excitability seen in the immediate period following MLR stimulation. It is speculated that the decrease in motoneuron excitability following the cessation of FL may be a result of metabotropic effects.



708.11/VV4. Variation in quipazine enhancement of flexor and extensor monosynaptic reflexes includes presynaptic and motoneuronal mechanisms
*J. W. CHOPEK, C. W. MACDONELL, K. E. POWER, K. GARDINER, P. F. GARDINER;
Spinal Cord Res. Centre, Physiol., Univ. of Manitoba, Winnipeg, MB, Canada
Serotonin (5-HT) is a well-known modulator of motor output, with the ability to increase or decrease the excitability of spinal reflexes through activation of 5-HT receptors. In particular, agonists of the 5-HT2R have been shown to increase the monosynaptic reflex (MSR) amplitude and to modulate the excitability of motoneurons (Mns). Whether quipazine, a 5HT2R agonist has a differential modulating effect on flexor and extensor motor output, is unknown. Measurements were taken of both the tibial (primarily extensor nerve) and the peroneal (primarily flexor nerve) MSR, properties of identified extensor and flexor Mns, and extracellular field potentials of both the extensor and flexor Ia pathways. All experiments were performed in vivo in an adult decerebrate rat preparation. The MSR was elicited by stimulating the L4/L5 dorsal roots and monitored by tibial (extensor) and peroneal (flexor) ENG. Measurements were taken pre- and post- injection of quipazine (I.P. injection 5mg/ml). The tibial and peroneal ENG showed a 3.76- and 5.97-fold increase in MSR amplitude, respectively, after quipazine administration, with the peroneal response showing a significantly larger increase than the tibial (p <0.05). In separate experiments, antidromically-identified extensor and flexor Mns were examined pre- and post- quipazine injection. Quipazine enhanced the overall excitability of Mns as evident by a 30% decrease in rheobase current, a 35% increase in input resistance, a shift of the frequency-current relationship to the left (i.e., higher frequencies for a given current) and an increase in the peak firing rate on a ramp current injection (p<0.05). As well, AHP amplitude was increased following quipazine administration (30% increase). No significant differences between flexor and extensor Mns pre- or post- quipazine injection were seen. Measurements of extracellular Ia field potentials of both the tibial and peroneal nerves pre- and post- quipazine injection suggested that the difference in excitability is at least partially presynaptic as evident by a larger increase in the peroneal field potential amplitude compared to that of the tibial (30% increase vs 7% increase). These data confirm that stimulation of 5-HT2R enhances the overall excitability of motor output, and demonstrates that the difference in enhancement of excitability seen between extensor and flexor motor output is due at least in part to presynaptic modulation in addition to modulation of motoneuron properties.



722.16/XX68. Semblions induced through inter-postsynaptic functional LINKs, biological parallels of K-lines, as basic units of internal sensations
*K. VADAKKAN;
Univ. of Manitoba, Winnipeg, MB, Canada
Reductionist approaches to determine the basic units that represent the internal sensations of memory and other higher brain functions necessitate the examination of their formation at physiological time-scales. During memory retrieval and hallucination, the activation of certain neurons at specific locations is reported. Experimental evidence shows activation of neuronal sets evoking different internal sensations. How does the firing of a neuron impart sensory meaning to the nervous system that it is a part of? An argument has been made that internal representation in the brain must play a substantive role (1). The present work derives the qualities of possible unitary sensory elements contributing to internal sensations. It is hypothesized that when multiple new sensory stimuli are activated together, a functional LINK is formed between the postsynapses of synapses that carry those different sensations such that the presentation of one of the stimuli will re-activate the functional LINK to activate the opposite postsynapse (2). It is also hypothesized that the resulting activation of the opposite postsynapse, in a system where neurons at certain neuronal orders fire in an oscillating mode, will induce a semblance of activity coming from the latter’s presynaptic terminal (2). The nature of this hallucination can be extrapolated towards the sensory receptor level to identify its sensory quality. Since large number of combinations (for spatial summation of EPSPs) and permutations (for temporal summation of EPSPs) of the neurons whose activity can give rise to an action potential, extrapolation in a retrograde fashion towards the sensory level will identify different sets of sensory receptors whose activation can theoretically cause the activation of a postsynapse. A hypothetical packet of minimum sensory stimuli, capable of activating one of the extrapolated sets of sensory receptors, namely semblion, is expected to be perceived by a nervous system when a specific postsynapse or neuron is activated. Integration of semblions using computational approaches can help elucidate the identities and nature of semblions that match with the internally generated sensations (2). The functional LINKs can be viewed as biological parallels of K-lines (3).
1. Sullivan J.A (2010) A role of representation in cognitive neurobiology. Philosophy of Science 77: 875-887
2. Vadakkan K.I (2011) Processing semblances induced through inter-postsynaptic functional LINKs, biological parallels of K-lines proposed for building artificial intelligence. Frontiers in Neuroscience
3. Minsky M (1980) K-Lines: A theory of memory. Cognitive Science: 4(2): 117-133



766.22/E2. Acetylcholine induces a hyperpolarization of voltage threshold in neonatal rat spinal motoneurons
*E. E. VASQUEZ-DOMINGUEZ, W. BAUTISTA, B. FEDIRCHUK;
Physiol., Univ. of Manitoba, Winnipeg, MB, Canada
Previous work has established that there is a dramatic increase in the excitability of mammalian spinal motoneurons prior to, and throughout motor activity. One property that is rapidly changed is the voltage threshold for action potential initiation (Vth), which is hyperpolarized (i.e. lowered), thereby facilitating motoneuron firing. Lowering of Vth has been observed in motoneurons during brainstem-induced fictive locomotion, and descending monoaminergic systems have been implicated in this effect. Recently however, we found Vth lowering also occurs during fictive scratch activity in acutely spinalized preparations. This suggests that in addition to descending systems, there is an intrinsic spinal neuromodulatory system able to regulate motoneuron Vth. Others have shown that cholinergic inputs to spinal motoneurons can alter their properties, but it is not clear whether they are able to modulate motoneuron Vth.
The aim of this study is to test the hypothesis that the cholinergic system can modulate motoneuron Vth. Whole-cell patch clamp recordings in either voltage or current-clamp configuration were obtained from lumbar motoneurons in in vitro neonatal rat spinal cord preparations (P0-4). Acetylcholine chloride (ACh) was applied to the extracellular solution in increasing concentrations (10-80 uM) and the motor output monitored using suction electrodes recording the L2 and L5 ventral roots bilaterally. In some experiments, synaptic blockers (AP5 20 uM, CNQX 10 uM, bicuculline 10 uM, strychnine 10 uM) were used to synaptically isolate the recorded motoneuron.
ACh induced Vth lowering in 7/8 motoneurons and ranged from a 4-26 mV effect. This robust Vth lowering occurred in both L2 and L5 motoneurons and was detectable in either voltage or current clamp. Vth lowering persisted with synaptic blockers in the bath and could occur in the absence of discernable network motor output. Confocal imaging of cords immunohistochemically processed for choline acetyl transferase (Chat) and PAN Nav revealed punctate cholinergic labeling in close proximity to motoneuron axon initial segments. This supports the idea that regulation of Vth may occur through focal cholinergic inputs projecting to the axon initial segment.
Overall, these results suggest that in addition to descending monoaminergic systems, a cholinergic system can lower Vth and thereby enhance motoneuron excitability. Future studies will determine whether this is the spinal system enhancing motoneuron excitability during motor output in acutely spinalized preparations.



775.27/U2. Phonemic perception in children with developmental dyslexia: An fMRI study
*L. CONANT1, E. LIEBENTHAL1,2, A. DESAI1, J. BINDER1;
1Neurol., Med. Col. of Wisconsin, Milwaukee, WI; 2Physiol., Univ. of Manitoba, Winnepeg, MB, Canada
Developmental dyslexia is a learning disability characterized by difficulties reading words accurately and/or fluently. Impairments in phonological processing, particularly phonological awareness, are widely considered to represent the core deficit in most cases of dyslexia. However, several behavioral studies in individuals with dyslexia have suggested the presence of a deficit at an earlier stage of processing, when the complex spectrotemporal patterns in the speech signal are analyzed and assigned to phonemic categories. This impairment in the categorical perception of phonemes could underlie a phonological awareness deficit in at least a subset of individuals with dyslexia. In this study, fMRI was used to compare brain responses associated with discrimination of CV syllables (P) and acoustically matched nonphonemic stimuli (N) in 8 children with dyslexia and 11 typically developing (TD) children, aged 8-17 years. The groups did not significantly differ in age or estimated nonverbal IQ but did differ on measures of reading and phonological processing. Discrimination performance confirmed that, in both groups, P stimuli were perceived categorically (better discrimination across than within phonemic categories) whereas N stimuli were not; however, the detection of across-category differences in P was poorer in the dyslexic group. In the P condition relative to N, the TD group showed greater activation in the left posterior superior temporal sulcus (pSTS) extending inferiorly into occipitotemporal regions, as well as in a smaller focus in the right pSTS. The dyslexia group showed greater activation in the bilateral insula, precentral gyri, supplementary motor area, and right postcentral and supramarginal gyri. This pattern of overactivation may suggest greater engagement of articulatory processes as well as the recruitment of additional right hemisphere regions to perform the phonemic discrimination task. These findings are generally consistent with several previous neuroimaging studies using print stimuli in individuals with dyslexia that found reduced activation in left temporoparietal and occipitotemporal regions and, more variably, increased activation in insular cortex and premotor/motor areas, as well as in additional right hemisphere regions. Thus, at this early stage of speech processing, group differences are already apparent in many of the regions implicated in dyslexia, suggesting that the primary deficit in at least a subset of children may lie earlier in the processing stream than phonological awareness and that categorical perception may be an important target of early intervention in children at risk for dyslexia.



868.01/D7. Properties of electrical synapses between Mesencephalic Trigeminal (MesV) neurons
*S. CURTI1, G. HOGE2, F. DAVOINE3, J. I. NAGY4, A. E. PEREDA2;
1Physiol., Sch. of Med., Montevideo, Uruguay; 2Dominick P. Purpura Dept. of Neurosci., Albert Einstein Col. of Med., Bronx, NY; 3Inst. de Ingenieria Electrica, Facultad de Ingenieria, Montevideo, Uruguay; 4Physiol., Univ. of Manitoba, Fac. of Med., Winnipeg, MB, Canada
We investigated the properties of electrical synapses between MesV neurons in the rat by combining whole cell patch clamp recordings with dye coupling and immunochemical analysis. Electrophysiological recordings showed an incidence of coupling of ~20%, and indicated that coupling could be unusually strong, with steady state coupling coefficients averaging ~0.1. Immunochemical analysis demonstrated that large areas of contact between MesV somata contain the gap junction protein connexin36 (Cx36), which presumably mediates electrical transmission between these neurons. Combining calculations of open channel number obtained from direct measurements of gap junctional conductance with estimates of the number of channels from confocal reconstructions of contact areas, suggest that less than ~1% of the channels might be open at a given time. Dye coupling experiments revealed that MesV neurons are coupled in pairs or triplets, a conclusion supported by analysis of intercellular connectivity based on labeling for Cx36. Frequency transfer analysis of these electrical synapses by injecting frequency-modulated sine wave (ZAP) currents to estimate coupling, revealed that these contacts do not behave as simple low pass filters. Moreover, transmission of high frequencies was found amplified, indicating that coupling of signals with high frequency contents, such as action potentials, might be relatively stronger. Because of its sensitivity to TTX and 4-AP, this property is likely to rely on persistent Na+ (INap) and A-type (IA) currents, which are prominent in these cells. We also found that coupling is developmentally regulated and, contrary to most examples, it increases with age. The incidence of dye coupling was virtually nonexistent before postnatal day 8, when it appears with its maximum incidence of ~25%. Interestingly, bursting, which critically relies on INap, is also regulated in an age-dependent manner with a time course comparable to that of coupling, suggesting a functional link between these two mechanisms. Accordingly, amplification of coupling potential by INap promoted lateral excitation and coincidence detection between pairs of coupled cells. Taken together our results suggest that electrical coupling is supported by a very small number of channels and that its interaction with intrinsic properties facilitate transmission of action potentials between MesV neurons, promoting strong and precise synchronization of pairs/triplets of neurons.



919.06/TT14. Neuromechanical model of spinal control of locomotion
*S. N. MARKIN1, A. N. KLISHKO2, N. A. SHEVTSOVA1, M. A. LEMAY1, B. I. PRILUTSKY2, D. A. MCCREA3, I. A. RYBAK1;
1Dept. Neurobio. and Anat., Drexel Univ. Col. of Med., PHILADELPHIA, PA; 2Sch. of Applied Physiol., Georgia Inst. of Technol., Atlanta, GA; 3Dept. Physiol., Univ. of Manitoba, Winnipeg, MB, Canada
A computational neuromechanical model of cat locomotion with two hindlimbs controlled by a locomotor spinal central pattern generator (CPG) and afferent feedback signals has been developed. The 2-D musculoskeletal model includes two 3-joint hindlimbs, pelvis, and trunk. Each hindlimb is actuated by nine Hill-type muscles including four bi-functional muscles: biceps femoris posterior (BFP), rectus femoris (RF), sartorius medial and gastrocnemius. The musculoskeletal model generates realistic group Ia, Ib and II muscle and cutaneous activity from muscle and paw pad afferents when recorded during locomotion muscle activity is used as input to the model. The architecture of spinal circuits and locomotor CPG is based on the model of the two-level model of locomotor CPG (Rybak et al. 2006) consisting of the flexor and extensor half-centers and pattern formation (PF) circuits. The model of PF circuits was extended to incorporate additional interneuron populations controlling the activity of bi-functional BFP and RF muscles. The neural model also includes basic reflex circuits mediating the reciprocal inhibition of antagonistic motoneurons via Ia inhibitory interneurons, recurrent inhibition via Renshaw cells, and di-synaptic excitation of extensors during stance phase of locomotion. The extended model of spinal circuits with the CPG shows the ability to generate the full repertoire of muscular activity patterns, including firing patterns of BFP and RF, observed during locomotion. The CPG operates under control of afferent feedback from muscles which stabilizes locomotor movement and controls locomotor phase transitions. The model demonstrates stable locomotion and exhibits realistic patterns of muscle activation, limb kinematics, and ground force dynamics. The model was used for investigation of the role of afferent feedback and the CPG for control of locomotion.



SAT057. Semblance Hypothesis of Memory: Computational Modelling and Development of Artificial Circuits
Satellite Organizer: *K. VADAKKAN;
Div. Neurology, Univ. of Manitoba, Winnipeg, MB, Canada
Location: 156
This presentation will demonstrate semblance hypothesis of memory that can explain how memories may be stored using synaptic plasticity changes and retrieved at physiological time-scales. A demonstration of the suitability of this hypothesis to explain various physiological and many pathological conditions will follow. Suitability of this hypothesis in explaining transfer of memories from the hippocampus to the cortex (consolidation), and correlation between memory and LTP will be explained. Special focus will be given to discuss computational modelling and electronic engineering methods to test the hypothesis. All SfN members are welcome. Space limited. Reservation appreciated. Contact: Kunjumon Vadakkan, Division of Neurology, University of Manitoba; (204) 998-8593; umvadakk@cc.umanitoba.ca; www.semblancehypothesis.org