Methods: Six-week-old buy LY2109761 (n = 12) and 14-week-old (n = 12) homozygous mutant

rats at the white spotting locus (Ws/Ws rat) were used. Rats were handled daily by the same person and submitted to water avoidance stress (WAS) daily for 13 days. Rats were exposed to stress session for 1 hr/day in the morning for 13 days and their fecal pellet output (FPO) were counted during WAS or sham WAS. Rats were euthanized after completion of stress experiment and whole colon was collected. Immunohistochemistry for mast cell tryptase and PAR-2 were performed in the proximal and distal PD0325901 price part of colon. Results: There was no difference in body weight change during stress experiment

between WAS and sham WAS group. WAS group exhibited increased FPO during 13 days compared to sham stress. This effect was significant for both aged Ws/Ws rat. MC were nearly absent in the colonic mucosa of 14-week-old Ws/Ws rat. In 6-week-old Ws/Ws rats, number of MC in the colonic mucosa were statistically increased by WAS compared to sham WAS. PAR-2 cells were statistically increased by WAS only in the 14-week-old Ws/Ws rat. Increased MC and PAR-2 cells by WAS were observed mainly in the proximal colon. Conclusion: Chronic psychological stress increased colonic motility independently to the presence

of mast cell in the colonic mucosa. And psychological stress increased not only mast cells but also other inflammatory cells preferentially in the proximal colon. Key almost Word(s): 1. Psychological stress; 2. mast cell; 3. colon; 4. Ws/Ws rat; Presenting Author: WANGZHI MO Additional Authors: HOUXIAO HUA Corresponding Author: HOUXIAO HUA Affiliations: Division of Gastroenterology, Union Hospital, Tongji Medical College Objective: To explore the role of SRF-IEG on the formation of visceral hypersensitivity induced by acute restraint stress. Methods: 12 male Sprague-Dawley rats were randomly divided into control group and acute restraint stress group (model group). Visceral hypersensitivity was made by acute restraint stress for 2 h. The colorectal distension (CRD) with different pressure were performed and abdominal withdrawal reflex (AWR) scores were observed during CRD. The visceral hypersensitivity was determined by AWR scores.