Contractile response of guinea pig ileum by repetitive application of morphine.
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.
Kusama
T
T
Department of Physiology and Anatomy, Nihon University College of Pharmacy, Chiba, Japan.
Murakoshi
Y
Y
Murakami
H
H
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
D011957:Receptors, Opioid; D009270:Naloxone; D013779:Tetrodotoxin; D009020:Morphine