Haemodynamic and baroreceptor responses to beta-adrenoceptor blocking agents in rabbits with cardiopulmonary bypass

Blood pressure and peripheral resistance were reduced, baroreceptor activity was enhanced after i.v. infusion of beta-adrenoceptor blocking agents in rabbits with intact circulation or with total cardiopulmonary bypass. The latter preparation allowed cardiac effects of the drugs to be excluded. In rabbits with an intact circulation, post-ganglionic sympathetic activity was reduced. These results suggest a direct vascular action of the drugs. The increased baroreceptor firing is not a cardiac-mediated effect and may partly induce the observed reduction in sympathetic activity.