title: Morphine antagonizes TRH-induced intestinal transit and hyperserotonemia in rabbits.
abstract: Thyrotropin releasing hormone (TRH), administered intracerebroventricularly (i.c.v.) in microgram quantities to anesthetized rabbits, produces marked stimulation of colonic motility, transit, and fluid accumulation, and is accompanied by a portal hyperserotonemia. In this study we found that pretreatment of rabbits with morphine (10 mg/kg i.v.) completely blocked the TRH-induced colonic transit and increase in luminal fluid, as well as the hyperserotonemia. A small dose of morphine (200 micrograms) given i.c.v., but not i.v., also inhibited the intestinal transit and portal hyperserotonemia. These results suggest that morphine inhibits TRH-induced intestinal transit and fluid accumulation, at least in part, by inhibition of a neural pathway mediating intestinal serotonin release.
mesh_terms: D000818:Animals; D001826:Body Fluids / Q000187:drug effects / Q000378:metabolism; D003106:Colon / Q000187:drug effects; D005772:Gastrointestinal Transit / Q000187:drug effects*; D066298:In Vitro Techniques; D007276:Injections, Intraventricular; D008297:Male; D009020:Morphine / Q000494:pharmacology*; D011817:Rabbits; D012701:Serotonin / Q000097:blood*; D013973:Thyrotropin-Releasing Hormone / Q000008:administration & dosage / Q000037:antagonists & inhibitors*
chemical_list: D012701:Serotonin; D013973:Thyrotropin-Releasing Hormone; D009020:Morphine