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ANTAGONISTIC EFFECT OF COMPOUND 48/80 ON THE INHIBITORY ACTIONS OF MORPHINE AND METHIONINE‐ENKEPHALIN ON ELECTRICALLY‐INDUCED CONTRACTIONS OF THE GUINEA‐PIG ILEUM
Author(s) -
KAMIKAWA YUICHIRO,
SHIMO YASUO
Publication year - 1978
Publication title -
british journal of pharmacology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.432
H-Index - 211
eISSN - 1476-5381
pISSN - 0007-1188
DOI - 10.1111/j.1476-5381.1978.tb17312.x
Subject(s) - ileum , chemistry , inhibitory postsynaptic potential , acetylcholine , medicine , cholinergic , endocrinology , compound 48/80 , antagonism , guinea pig , antagonist , muscarinic acetylcholine receptor , morphine , muscle contraction , pharmacology , receptor , biology , biochemistry , degranulation
1 The effect of compound 48/80 was studied on the twitch‐like contractions of the longitudinal muscle of guinea‐pig ileum induced by electrical stimulation of intramural cholinergic nerves. 2 Compound 48/80 alone, at concentrations up to 30 μg/ml, had no effect on the twitch contractions. The contraction to exogenously applied acetylcholine was slightly depressed by the compound. 3 At 100 μg/ml, compound 48/80 caused a weak but long‐lasting increase in tone and irregular contractile activity in the ileum, part of which was reduced but not completely abolished by pretreatment with chlorpheniramine (1 μ m ) or by repeated applications of compound 48/80. 4 The inhibitory effects of morphine and methionine‐enkephalin on the twitches were antagonized by the presence of compound 48/80 (3 to 30 μg/ml), possibly in a competitive manner. The antagonism was not affected by pretreatment with the antihistaminics, chlorpheniramine and/or metiamide. 5 The inhibitory effects of noradrenaline and adrenaline on the twitches were slightly but significantly increased by the presence of compound 48/80 (10 or 30 μg/ml), whereas that of ATP was not modified. 6 These results indicate that compound 48/80 acts as a selective and competitive antagonist at opiate receptors located in the intramural cholinergic nerves of guinea‐pig ileum.