Effect of dopamine on dog distal colon in-vitro

Abstract

The effects of dopamine, isoprenaline, adrenaline and noradrenaline in dog isolated colon strips were studied. All these drugs produced in the preparation relaxations which were inhibited by propranolol and sotalol or, in the case of noradrenaline, by a mixture of propranolol and phentolamine. A selective β1-adrenergic antagonist, practolol, had the same inhibitory effects on the relaxations induced by all the agonists, suggesting the existence of β1- and β2-adrenoceptor subtypes in the dog distal colon. There is no evidence for the presence of specific dopaminergic receptors in this preparation.