Potentiation of beta-sympathomimetics with alpha-adrenoceptor blocking drugs in guinea pig trachea and human bronchus preparations.

The actions of beta-sympathomimetics alone and in various combinations with alpha-adrenoceptor blocking agents were studied in guinea pig tracheal chain and in some preparations of human bronchi taken in operations. All the alpha-adrenoceptor blockers caused 50-100% potentiation of the effects of the beta-sympathomimetics studied in both preparations, had no effects of their own in the rather low concentrations used (10(-10) --10(-6) mol/l). The results show that guinea pig and human tracheobronchial smooth muscle react similarly to these drugs and may contain adrenergic alpha-receptors.