EFFECT OF COLD-RESTRAINT STRESS ON IMMUNOREACTIVE THYROTROPIN-RELEASING-HORMONE AND IMMUNOREACTIVE SOMATOSTATIN IN THE RAT STOMACH

The effects of cold-restraint stress on immunoreactive thyrotropin-rel easing hormone (ir-TRH) and immunoreactive somatostatin (ir-SOM) conce ntrations in the rat stomach were investigated. Rats immobilized with a spring-loaded metallic plate were placed in a room maintained at 4 d egrees C for 1-3 h and then decapitated serially for investigation. Ga stric ir-TRH and ir-SOM concentrations were measured by individual rad ioimmunoassays. Cold-restraint stress induced gastric mucosal lesions as well as a decrease of the ir-TRH concentration in the glandular sto mach, an increase of the ir-TRH concentration in the gastric juice, an d a decrease in gastric pH. In contrast, this stress caused an increas e of ir-SOM in the glandular stomach and a decrease of ir-SOM in the g astric juice. However, cold or restraint stress alone did not induce g astric mucosal lesions or changes in gastric ir-TRH and ir-SOM concent rations or the gastric pH. To clarify the endocrine influence of perip heral TRH, pretreatment with thyroid hormone was performed to inhibit elevation of the serum TRH level during cold-restraint stress. Despite this pretreatment, cold-restraint stress still induced ulcer formatio n, along with changes in gastric ir-TRH and ir-SOM concentrations and gastric pH. These findings suggest that changes in gastric ir-TRH and ir-SOM concentrations may be closely related to ulcer formation due to cold-restraint, and that TRH may act in a paracrine manner in the sto mach.