[Mechanism of action of catecholamines on the electrically-stimulated, isolated guinea-pig gallbladder].
Effects of catecholamines on the contraction of isolated guinea-pig gallbladder induced by transmural stimulation (TM) were investigated. Tetrodotoxin and atropine prevented the TM-induced contraction. Atropine, but not tetrodotoxin, blocked the acetylcholine-induced contraction. Furthermore, the TM-induced contraction was sharply reduced during a cold storage for 1 to 4 days and then abolished 4 to 7 days later. Norepinephrine (5 X 10(-6) M) and epinephrine (4.5 X 10(-6) M) did not affect acetylcholine-induced contraction, but reduced the contractile response to TM by about 40% and 60%, respectively. Phentolamine, but not propranolol, abolished the inhibitory effects of norepinephrine and epinephrine on the contraction induced by TM. Isoproterenol and phenylephrine did not significantly modify the TM-induced contraction. These observations suggest that TM-induced contraction is produced by the release of acetylcholine from the ending of postganglionic cholinergic fibers. The possibility that norepinephrine and epinephrine act on the inhibitory alpha-adrenoreceptors in the ending of cholinergic neuron is discussed.
D000109:Acetylcholine / Q000494:pharmacology; D000818:Animals; D002395:Catecholamines / Q000494:pharmacology*; D004558:Electric Stimulation; D005260:Female; D005704:Gallbladder / Q000187:drug effects*; D006168:Guinea Pigs; D066298:In Vitro Techniques; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects; D009130:Muscle, Smooth / Q000187:drug effects
D002395:Catecholamines; D000109:Acetylcholine
Untersuchungen zum Wirkungsmechanismus von Katecholaminen an der elektrisch gereizten isolierten Meerschweinchen-Gallenblase.