Abstract
The influence of selective β 2-adrenoceptor stimulation and blockade on cardiac electrophysiologic properties was studied in 18 anesthetized dogs. Selective β 2-adrenoceptor activation by salbutamol failed to alter myocardial excitability but significantly lowered serum potassium concentration. Excitability, refractoriness, and ventricular fibrillation threshold were also not changed after administration of 100 and 200 μg/kg of the selective β 2-antagonist ICI 118,551. However, at a dose of 500 μg/kg, refractoriness was prolonged and ventricular fibrillation threshold increased. These changes appear to be due to blockade of β 1-adrenoceptors rather than to membrane stabilizing effects, since in catecholamine-depleted animals even the highest dose of ICI 118,551 did not alter myocardial electrical properties. It is concluded that β 2-adrenoceptors do not influence electrophysiologic properties of the canine myocardium.
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