AGA Abstracts (group 3 and group 4) compared to group 1 and group 2 (p<0.01). Overall, the rats with neonatal acid exposure and rechallenged in adulthood (group 4) exhibited the highest expression of NR1 and PSD-95. CONCLUSIONS: Early life esophageal acid exposure accentu- ates the expression of NR1 and PSD-95 in ACC neurons in response to acid rechallenge in adulthood. This neuronal plasticity in the ACC circuitry may be responsible for enhanced nociceptive transmission in visceral hypersensitivity. S1804 Modulation of Spinal Glia Activation and Glutamate Transmission in the Model of Chronic Water Avoidance Stress-Induced Visceral Hyperalgesia: Role of Glucocorticoids Sylvie Bradesi, Helena S. Ennes, Iordanis Karagiannidis, Bakirtzi Kyriaki, James A. McRoberts, Charalabos Pothoulakis, Emeran A. Mayer BACKGROUND: Spinal glia play an important role in the development of hyperalgesia in neuropathic and inflammatory pain models. We recently demonstrated that spinal glia are also involved in visceral hyperalgesia in a model of chronic stress in rats (Bradesi et al. Gastroenterology 2009). Spinal glia (mostly astrocytes) plays a major role in the clearance of synaptic glutamate (GLU) via high affinity glutamate reuptake transporters (GLT1) and GLT1 expression has been shown to be affected by glucocorticoids in cultured glia from rat cortex (Jacobsson et al. 2006) AIMS: We aimed to study 1) the effect of chronic WA stress on the spinal GLU signaling system and 2) the role of stress-induced glucocorticoids (GCs) in this process and in the development of visceral hyperalgesia. METHODS: Groups of male Wistar rats were exposed to chronic WA (1 hour/day/10 days) or sham WA and treated with the GC receptor antagonist RU486 either subcutaneously (s.c) 25 mg/kg, 2 hours before WA or sham WA every 2 days or intrathecally (i.t.) 4 microg/rat/day infused via chronic osmotic minipumps. On day 11, L6-S1 spinal cord segments were collected and processed for western blotting (WB) for P-p38 (phosphorylated p38), GLT1, NR1 and P- NR1. NR2 and PNR2 were measured by immunoprecipitation. mRNA levels of NR1 and NR2A/B were measured by real time RT-PCR. Different groups of rats were equipped for recording of the visceromotor response (VMR) to colorectal distension (CRD) which was recorded on day 0 and on day 11. RESULTS: P-p38 was increased after WA compared with sham WA and this effect was blocked by s.c. and i.t. RU486 treatments (P<0.05). GLT1 protein expression was reduced in WA rats compared with controls and this effect was blocked after RU 486 s.c. (P<0.05) or i.t.. The mRNA expression of NR1 and NR2 was not significantly different in WA compared with sham WA. Similarly, the protein level or the phosphorylation of NR1 (P-Ser) or NR2 (P-Tyr) was unchanged across the different groups. Rats exposed to WA stress showed increased VMR to CRD at day 11 (P<0.05) compared with baseline, consistent with visceral hyperalgesia. This effect was blocked by RU486 administered s.c or i.t. (P<0.05). RU486 had no effect in sham WA rats. CONCLUSIONS: Stress-induced GC changes are involved in: A) the signaling pathways leading to stress- induced spinal glia activation (P-p38); B) the modulation of GLT1 expression, and C) in stress-induced visceral hyperalgesia. In contrast to a previous report showing GC modulation of NMDARs expression in a model of peripheral nerve injury (Wang et al, 2005 , we found that chronic WA does not affect NMDAR expression or its phosphorylation. S1805 Neuroendocrine Responses to Somatic Pain Stimuli in IBS Patients QiQi Zhou, Kara L. Dreher, G Nicholas Verne Background: Previous studies have shown dysregulation of the hypothalamic-pituitary- adrenal (HPA) axis in the irritable bowel syndrome (IBS). A recent study by Chang et al., demonstrated stimulated cortisol and corticotrophin responses to a visceral pain stimulus (Chang et al., 2009). However, no studies to date have evaluated neuroendocrine responses to diverse somatic pain stimuli in IBS patients. In the current study, we determined if there were significant neuroendocrine responses to multiple experimental somatic pain stimuli in IBS patients. Methods: To accomplish this, we evaluated sensory affective ratings and changes in cortisol and corticotrophin in response to contact thermal, mechanical pressure, cold pressor, and ischemic experimental pain stimuli in 68 diarrhea-predominant IBS patients and 40 healthy controls. Serum cortisol and corticotrophin levels were drawn at baseline and then immediately after each experimental pain procedure. Levels of cortisol and cortico- trophin were determined using commercially available radioimmunoassay kits (Siemens Medical Solutions Diagnostics, Los Angeles, CA). A 60-minute rest period in the semi- recumbent position was conducted between experimental pain stimuli to allow neuroendoc- rine responses to normalize to baseline. One way ANOVA followed by Tukey comparison was used to analyze the changes in cortisol and corticotrophin levels. Results: A subset of IBS patients had hypersensitivity to experimental thermal (35%), cold pressor (29%), and ischemic pain (41%) stimuli (p<0.05). There were significant increases in cortisol and corticotrophin levels in IBS patients but not in controls following the ischemic pain stimuli (p<0.05). Both cortisol and corticotrophin levels increased in IBS patients following the cold pressor test, however, the increases did not reach statistical significance (p<0.08). There were no differences in cortisol or corticotrophin levels following the thermal and mechanical pain stimuli. IBS patients demonstrate increased neuroendocrine responses to ischemic and cold pressor experimental pain stimuli. These findings support dysregulation of the HPA axis in a subset of IBS patients with hypersensitivity to experimental somatic pain stimuli. S1806 Experimentally Induced Colitis Modulates the Release of Nerve Growth Factor and Brain-Derived Neurotrophic Factor in the Pelvis via TRPV1 Related Pathways Xiao-Qing Pan, Jessica A. Gonzalez, Anna P. Malykhina Background: Neurotrophins have been shown to act as pain modulators, particularly in inflammatory pain states. Nerve growth factor (NGF) is considered as a peripheral modulator of pain. In nociceptors NGF regulates the expression of a second neurotrophin, brain-derived S-278 AGA Abstracts neurotrophic factor (BDNF) which is known as a central modulator of pain. In this study we tested the hypothesis that desensitization of TRPV1 receptors in the colon can affect the release of neurotrophins NGF and BDNF in the pelvis after experimentally induced colitis. Methods: Four groups of animals (males, Sprague-Dawley rats) were included in the study: 1- control group, 2 - trinitrobenzene sulfonic acid (TNBS) induced colitis, 3 - intracolonic resiniferatoxin (RTX) instillation and 4 - RTX followed by TNBS (2 days after RTX). Desensit- ization of TRPV1 receptors was achieved by intracolonic application of RTX (10-7 M). Tissue samples were collected from the distal colon, urinary bladder, lumbosacral (L6-S2) segments of the spinal cord and dorsal root ganglia (DRG). The mRNA level and protein concentrations of NGF and BDNF were measured at 3, 5 and 30 days post-TNBS. Results: RTX instillation in the distal colon caused a 2-fold up-regulation of NGF at both mRNA and protein levels in the colon at day 3 (n=7, p≤0.05) followed by recovery to the control values at later time points. RTX treatment did not affect gene expression nor protein concentration of NGF during acute colitis in the spinal cord. In DRG phasic dynamics was observed: at day 3 mRNA level of NGF was decreased by 36 % (n= 5, p≤0.05) followed by 59% increase at day 5 (n=4, p≤0.05) and then returned to low level by day 30. Activation of TRPV1 signaling in the distal colon increased the concentration of NGF protein in the urinary bladder by 50-70% at days 3 and 5 post-RTX, whereas TNBS-induced colitis caused even more significant changes (2-2.5 fold increase in the level of NGF protein). However, combined treatment (RTX+TNBS) showed no changes in the bladder when compared to the control values. BDNF mRNA was undetectable in both pelvic organs. Colonic inflammation did not affect the protein concentration of BDNF in the bladder but caused a 3-fold decrease at day 30 post-TNBS (n=5, p≤0.05) in the inflamed colon. Conclusion: Our results provide evidence that activation of TRPV1 signaling cascade modifies the gene and protein expression of neurotrophins NGF and BDNF in the pelvis. Understanding the molecular physiology of neurotrophin release has the potential to advance the generation of new pharmacological therapies for the treatment of functional pelvis. This work was supported by NIH grants DK077699 and DK077699-S2 (ARRA). S1807 Repeated Psychological Stress-Induced Alterations of Visceromotor Response (VMR) to Colorectal Distension (CRD) and Defecation in Mice: Influence of Surgery and Postoperative Single Housing Muriel H. Larauche, Guillaume Gourcerol, David W. Adelson, Mulugeta Million, Yvette Tache Background: Visceral pain modulation by chronic stress in mice has been little studied. Electromyography (EMG) recording of abdominal muscle contractions, as a proxy to VMR, requires electrode implantation and post-surgical single housing (SH) which could affect stress-induced VMR changes. Aims: To assess repeated psychological stress influence on visceral sensitivity in mice subjected to EMG surgery (S) plus single housing (S-SH) or no surgery (NS) plus single (NS-SH) or group housing (NS-GH). Methods: Male C57Bl/6 mice (25-30g) were used. The validation of VMR monitoring based on intracolonic pressure (ICP) measure via a miniaturized pressure transducer inserted acutely into the distal colon, was performed by simultaneously recording EMG and ICP signals induced by phasic CRD (15, 30, 45, 60 mmHg, 3 times each, 10 sec, 4 min interval), on the same S-SH mouse (n=9), 5 days post-surgery. Then using the ICP method we monitored the baseline VMR to a 1 st CRD, before splitting mice in S-SH (n=13), NS-SH (n=10) and NS-GH (n=18) groups, subjecting them repeatedly to water avoidance stress (WAS, 1h/day, 10 days), and recording the VMR to a 2 nd CRD 24 h after the last WAS. Defecation was monitored daily during WAS and additional S-SH (n=5), NS-SH (n=13) and NS-GH (n=4) groups (no WAS, no CRD) were used to assess basal non-stressful defecation in home cage. Results: When assessed simultaneously in conscious mice, CRD-induced EMG and ICP responses exhibited a strong correlation (R 2 = 0.862, p<0.05) and detected similar pain threshold pressure (31.4 ± 1.3 vs. 32.4 ± 2.2 mmHg, respectively, p>0.05). The baseline VMR to CRD was similar between groups. WAS increased VMR at 60 mmHg in S-SH group and decreased it at 30-60 mmHg in NS-GH mice, while having no effect in NS-SH mice. Daily basal non stressful defecation did not differ between groups however WAS increased significantly the average defecation in S-SH vs NS-GH and NS-SH mice (6.4 ± 1.0 vs 3.1 ± 0.4 and 3.1 ± 1.0 pellets/h/day respectively, p<0.05). Conclusions: Using a novel non-invasive method to monitor VMR in conscious mice that we developed and validated, we found colonic motor and visceral functions alterations in response to a repeated psychological stress in S-SH mice but not in NS-SH and NS-GH mice. These data suggest that the combination of surgery and single housing required for EMG-monitoring of VMR can affect the responsiveness of mice to an additional stressor, raising the need to reassess the classical methods employed to evaluate visceral sensitivity in mice. Support: NIH P50 DK-64539 (YT), DK AM 41301 (YT, MM), DK- 78676 (MM), T32 DK07180-33 (ML), French Society of Gastroenterology (GG) S1808 Analgesic Effect of URB597, a Selective Inhibitor of Fatty Acid Amide Hydrolase (FAAH) on Colorectal Pain in a Rat Model of Irritable Bowel Syndrome (IBS) Induced by the Selective Corticotropin Releasing Factor Receptor 1 (CRF 1 ) Agonist, Cortagine Muriel H. Larauche, Chrysanthy Ha, Mulugeta Million, Peter Germano, James P. Pearson, Yvette Tache Background: The endocannabinoid (eCB) signaling system, including eCBs (anandamide [AEA] and 2-arachidonoyl glycerol [2-AG]), cannabinoid receptors (CB 1 and CB 2 ), and degradation pathways (FAAH and monoacylglycerol lipase [MAGL] enzymes), is present in the central and enteric nervous systems. Recent evidence points to components of the eCB system being altered in functional gastrointestinal disorders. Aim: To investigate the effect of systemic FAAH inhibitor treatment on visceral hypersensitivity in a rat model of diarrhea- predominant IBS (IBS-D) symptoms induced by cortagine (AJP 297:G215-G227, 2009). Methods: Male Sprague-Dawley rats were habituated to Bollman cages for 3 days. The following day, rats were anesthetized with isoflurane and a 5 cm balloon pressure sensor was inserted into the distal colon 1 cm from the anus. After 20 min, a first colorectal distension (CRD) baseline was performed (10, 20, 40, 60 mmHg, 20 s duration, 4 min