Endogenous angiotensin II and bradykinin delay and attenuate the hypotension after N-type calcium channel blockade in conscious rabbits

Abstract

The effects of N-type calcium channel inhibition with ω-conotoxin GVIA (ω-CTX) on cardiovascular parameters and vagally mediated autonomic reflexes and the role of the renin-angiotensin system were assessed in conscious rabbits. ω-CTX (10 μg/kg, i.v.) resulted in hypotension, tachycardia, and attenuation of the sympathetic and vagal components of the baroreceptor- heart rate reflex (baroreflex). In the control group (no pretreatment), the peak decrease in mean arterial pressure (MAP) of 13 μ 3 mm Hg from 72 μ 2 mm Hg occurred after 33 μ 3 min, with a corresponding tachycardia of 80 μ 20 beats/min (n = 6). The tachycardia was due to vagal withdrawal, as a similar increase in heart rate (84 μ ..