Morphine inhibits TRH-induced intestinal transit increases.
The current study examined the effects of intraperitoneal (IP) and intracisternal (IC) administration of the opiate agonist, morphine, and an opioid, central beta-endorphin, on thyrotropin releasing hormone (TRH)-induced small intestinal transit increases. Anesthetized rats, 14-day and older, were studied to determine age-related differences. Results showed that in all age groups IP morphine (2 mg/kg) blocked TRH (15 micrograms)-induced increases in transit of a charcoal bolus. Morphine 1 microgram and beta-endorphin 1 microgram administered IC in 0.6 microliter failed to block TRH (10 microgram)-induced increases in intestinal transit in 14-day-old rats. However both morphine and beta-endorphin 1 micrograms IC blocked TRH-induced increases in adult rats. Dose-response studies demonstrated that higher doses (greater than 1 microgram) of morphine IC were required to block TRH-induced increases in preweaning rats.
Heitkemper
M M
MM
Department of Physiological Nursing, University of Washington, Seattle 98195.
Bond
E F
EF
D000375:Aging / Q000502:physiology; D000818:Animals; D002946:Cisterna Magna; D005260:Female; D005772:Gastrointestinal Transit / Q000187:drug effects*; D007267:Injections; D007274:Injections, Intraperitoneal; D008297:Male; D009020:Morphine / Q000494:pharmacology*; D051381:Rats; D011919:Rats, Inbred Strains; D013973:Thyrotropin-Releasing Hormone / Q000037:antagonists & inhibitors*; D001615:beta-Endorphin / Q000494:pharmacology*
D013973:Thyrotropin-Releasing Hormone; D001615:beta-Endorphin; D009020:Morphine