Depressant effects of phenoxygenzamine on potassium contracture in cat ventricular muscle.

Phenoxybenzamine has been shown to have a depressant action on K+-depolarization contracture in cat ventricular muscle. In the present study, we show that this depressant action is specific for phenoxybenzamine and occurs in the presence of beta-adrenergic receptor blockade with nadolol. K+-contracture is not depressed by phentolamine nor augmented by phenylephrine. Thus, the depressant action of phenoxybenzamine is not mediated by its effects on cardiac adrenergic receptors.