title: Contractile response of guinea pig ileum by repetitive application of morphine.
abstract: 1. The repetitive application of morphine gradually induced a contracture in the isolated guinea pig ileum. 2. The optimum conditions for induction of the contracture were as follows: the concentration, incubation time and washout time of morphine were 1 or 10 microM, 2 and 3 min, respectively. 3. Preincubation with naloxone or TTX blocked this morphine-induced contracture. 4. Among twitch-inhibiting drugs, only clonidine induced a contracture similar to that induced by morphine, while tetrodotoxin (TTX) and adenosine did not. 5. The contracture was also observed in the longitudinal muscle-myenteric plexus preparations. 6. These findings indicate that morphine has a dual inhibitory and excitatory action on the guinea pig ileum and that its repetitive application preferentially diminish the inhibitory one.
authors.affiliation: Department of Physiology and Anatomy, Nihon University College of Pharmacy, Chiba, Japan.
authors.forename: T
authors.initials: T
authors.lastname: Kusama
authors.forename: Y
authors.initials: Y
authors.lastname: Murakoshi
authors.forename: H
authors.initials: H
authors.lastname: Murakami
mesh_terms: D000818:Animals; D006168:Guinea Pigs; D007082:Ileum / Q000187:drug effects; D066298:In Vitro Techniques; D008297:Male; D009020:Morphine / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D009119:Muscle Contraction / Q000187:drug effects; D009131:Muscle, Smooth, Vascular / Q000187:drug effects*; D009197:Myenteric Plexus / Q000187:drug effects; D009270:Naloxone / Q000494:pharmacology; D011957:Receptors, Opioid / Q000187:drug effects; D013779:Tetrodotoxin / Q000494:pharmacology
chemical_list: D011957:Receptors, Opioid; D009270:Naloxone; D013779:Tetrodotoxin; D009020:Morphine