[Pharmacological studies of loperamide, an anti-diarrheal agent. III. Interaction between loperamide and various agonists in the guinea pig intestine (author's transl)].
To clarify the mode of action of loperamide, the interaction with various agonists was investigated in guinea pig intestines. The following results were obtained. Prostaglandin E1 (0.1 microgram) or acetylcholine (1 approximately 3 microgram) injection into the mesenteric artery at 10 min intervals caused a constant rise of intraluminal pressure of the intestinal loop in situ. Loperamide (0.01 approximately 0.1 mg/kg i.v.) markedly suppressed the response induced by prostaglandin E1. Morphine (0.1 approximately 1.0 mg/kg i.v.) and atropine (0.01 mg/kg i.v.) also suppressed the response. The intestinal response induced by acetylcholine was inhibited markedly by atropine and slightly by loperamide (0.1 mg/kg i.v.) but not by morphine. Contractions of the isolated ileum induced by coaxial stimulation, BaCl2, nicotine and serotonin were suppressed by loperamide (10(-9) approximately 2 X 10(-7) g/ml). Morphine, methadone and codeine showed the same effect as loperamide but the activity was weaker than that of loperamide. Contractions of isolated ileum induced by acetylcholine, histamine and bradykinin, and Ca-contraction in the depolarized taenia coli were inhibited by relatively high concentrations of loperamide (2 X 10(-7) g/ml or above). These results suggest that loperamide suppresses the function of cholinergic neurons in the intestines.
D000109:Acetylcholine / Q000037:antagonists & inhibitors*; D000818:Animals; D000930:Antidiarrheals; D001464:Barium / Q000037:antagonists & inhibitors; D001920:Bradykinin / Q000037:antagonists & inhibitors; D002118:Calcium / Q000037:antagonists & inhibitors; D006168:Guinea Pigs; D006633:Histamine Antagonists; D007082:Ileum / Q000187:drug effects; D066298:In Vitro Techniques; D007422:Intestines / Q000187:drug effects*; D008139:Loperamide / Q000494:pharmacology*; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects; D009130:Muscle, Smooth / Q000187:drug effects; D009538:Nicotine / Q000037:antagonists & inhibitors; D010812:Physical Stimulation; D010880:Piperidines / Q000494:pharmacology*; D011458:Prostaglandins E / Q000037:antagonists & inhibitors*; D012702:Serotonin Antagonists
D000930:Antidiarrheals; D006633:Histamine Antagonists; D010880:Piperidines; D011458:Prostaglandins E; D012702:Serotonin Antagonists; D001464:Barium; D009538:Nicotine; D008139:Loperamide; D000109:Acetylcholine; D001920:Bradykinin; D002118:Calcium