INHIBITORY EFFECT OF ETHANOL ON THE 5-HT3 RECEPTOR-MEDIATED TACHYCARDIA IN ISOLATED GUINEA-PIG ATRIUM

The influence of ethanol on 5-hydroxytryptamine (5-HT)-induced tachyca rdia mediated by 5-HT3 receptor activation in the isolated guinea-pig atrium was studied. Ethanol at 200 mM significantly inhibited 5-HT-but not isoproterenol- or histamine-induced tachycardia in the isolated g uinea-pig atrium. The same inhibitory effect was observed in response to 2-propanol and chloral hydrate application. Both 2-propanol at 100 mM and chloral hydrate at 1 mM exhibited inhibitory effects on 5-HT-in duced tachycardia as potent as those of ethanol at 200 mM. These alcoh ols did not inhibit the tachycardia induced by isoproterencl or histam ine. The inhibitory effects of the alcohols seemed to be specific for 5-HT and to increase according to their lipophilicity. Our results sug gest that the inhibitory effects of ethanol on 5-HT3 receptor-mediated tachycardia are related to the direct effect of ethanol on 5-HT3 rece ptors in the atrium.