Haemodynamic effects of the quaternary ammonium compound QX 572 in anaesthetized cats. III. Interactions with adrenergic beta-adrenoceptor blockade.

The positive cardiac chronotropic effects of the antiarrhythmic compound, QX 572, in anaesthetized cats has been shown mainly to be due to a release of catecholamines from sympathetic nerve-endings. Furthermore, these undesired effects of QX 572 on heart rate were decreased by adrenergic beta blockade in the animals. In the present study it was found that an adrenergic beta-blockade did not reveal any cardiodepressive effects of QX 572, that in the normal animals might have been masked by the effects of the drug-induced catecholamine-release.