MODE OF THE BRONCHODILATOR ACTION OF PHENTOLAMINE

The alpha adrenergic blocking agent, phentolamine, displays prominent bronchodilator activity in guinea pigs. This action was maintained after acute denervation of the adrenal glands, but it was suppressed by the beta adrenergic blocking agent sotalol (MJ 1999) and to a lesser extent by adequate dosage of P-286. The latter drug did not significantly influence the bronchodilator action of exogenous epinephrine, but it has been reported to block the release of epinephrifle from the adrenal medulla. It is suggested that the bronchodilator action of phentolamine in the guinea pig is due mainly to the release of epinephrine from the adrenal medulla or other storage sites.