Indirect intestinal stimulatory effects of heroin: direct action on opiate receptors.
The effects of bolus intra-arterial doses of heroin and other stimulant drugs were studied in vascularly perfused isolated segments of dog small intestine. Heroin caused dose-related increases in intraluminal pressure similar in appearance to those caused by morphine. Perfusion with Krebs bicarbonate solution containing naloxone selectively abolished intestinal responses to heroin. Perfusion with cinanserin, a 5-hydroxytryptamine (5-HT) antagonist, decreased intestinal responses to 5-HT and heroin without affecting responses to dimethylphenylpiperazinium (DMPP) or bethanechol (BeCh). Tetrodotoxin reduced responses to heroin, 5-HT and DMPP but not responses to BeCh. Atropine antagonized contractile responses to all 4 stimulatory agents. These data indicate that heroin interacts with a conventional opiate receptor in the intestine and that the intestinal stimulatory effect of heroin is mediated by the release of endogenous 5-HT which activates intramural cholinergic neurons.
D000818:Animals; D001285:Atropine / Q000494:pharmacology; D001626:Bethanechol Compounds / Q000494:pharmacology; D002928:Cinanserin / Q000494:pharmacology; D004246:Dimethylphenylpiperazinium Iodide / Q000494:pharmacology; D004285:Dogs; D005260:Female; D003932:Heroin / Q000494:pharmacology*; D007422:Intestines / Q000187:drug effects*; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects; D009130:Muscle, Smooth / Q000187:drug effects; D009270:Naloxone / Q000494:pharmacology; D011957:Receptors, Opioid / Q000187:drug effects*; D013268:Stimulation, Chemical; D013779:Tetrodotoxin / Q000494:pharmacology
D001626:Bethanechol Compounds; D011957:Receptors, Opioid; D009270:Naloxone; D013779:Tetrodotoxin; D004246:Dimethylphenylpiperazinium Iodide; D003932:Heroin; D001285:Atropine; D002928:Cinanserin