INFLUENCE OF ANGIOTENSIN-II ON THE ALPHA-ADRENOCEPTORS INVOLVED IN MEDIATING THE RESPONSE TO SYMPATHETIC-NERVE STIMULATION IN THE RABBIT ISOLATED DISTAL SAPHENOUS ARTERY

Under normal experimental conditions, sympathetic nerve-mediated responses to electrical field stimulation in the isolated distal saphenous artery of the rabbit are sensitive to prazosin (0.1-mu-M) and so, by definition, are mediated by alpha-1-adrenoceptors. In the presence of angiotensin II (A II, 0.05-mu-M) however, a component of the response to nerve stimulation became resistant to prazosin. This 'uncovered' response was virtually abolished by the selective alpha-2-adrenoceptor antagonist rauwolscine (1-mu-M), a concentration that in the absence of A II had enhanced nerve-mediated responses. Exposure to A II therefore, allows the clear demonstration of a role for postjunctional alpha-2-adrenoceptors in mediating the contractile response to sympathetic nerve stimulation in this arterial preparation.