The inhibitory effect of dopamine on cat gastric smooth muscle.
The inhibitory effect of dopamine has been studied in longitudinal and circular muscle strips of the cat gastric fundus. When tone was raised by transmural electrical stimulation and by administration of methacholine, dopamine concentration-dependently relaxed the strips but the inhibitory effect of dopamine was clearly more pronounced on electrically-induced tone. The effect of dopamine was not influenced by the presence of cocaine or hydrocortisone. The relaxant effect of dopamine, when tone was raised by methacholine, was not influenced by alpha- and dopamine receptor antagonists but it was significantly reduced by propranolol and ICI 118551 (erythro-DL-1-(7-methylindan-4-yloxy)-3- isopropylaminobutan-2-ol). The inhibitory effect of dopamine on the electrically-induced tone was significantly reduced by phentolamine; domperidone tended to reduce the effect of the lower concentrations of dopamine. In the presence of propranolol, phentolamine and rauwolscine concentration-dependently antagonized the inhibitory effect of dopamine on electrically-induced tone, while prazosin was without influence. These results indicate that the inhibitory effect of dopamine in the cat gastric fundus is mainly due to interaction with postjunctional beta 2-adrenoceptors on the smooth muscle cells and with prejunctional alpha 2-adrenoceptors on the intramural cholinergic neurons.
Heymans Institute of Pharmacology, University of Gent Medical School, Belgium.
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Lefebvre
D000317:Adrenergic alpha-Antagonists / Q000494:pharmacology; D000319:Adrenergic beta-Antagonists / Q000494:pharmacology; D000818:Animals; D002415:Cats; D004294:Domperidone / Q000494:pharmacology; D004298:Dopamine / Q000494:pharmacology*; D018492:Dopamine Antagonists; D004558:Electric Stimulation; D005260:Female; D066298:In Vitro Techniques; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects; D009130:Muscle, Smooth / Q000187:drug effects*; D013270:Stomach / Q000187:drug effects*
D000317:Adrenergic alpha-Antagonists; D000319:Adrenergic beta-Antagonists; D018492:Dopamine Antagonists; D004294:Domperidone; D004298:Dopamine