PLASMA-RENIN ACTIVITY DURING HYPOTENSIVE RESPONSES TO ELECTRICAL-STIMULATION OF CAROTID-SINUS NERVES IN CONSCIOUS DOGS

1. The interaction of electrical stimulation of the carotid sinus nerv es (carotid sinus nerve stimulation, CSNS) with mechanisms of renin re lease was studied in conscious and unrestrained resting beagle dogs re ceiving a standardized diet (sodium intake, 4.5 mmol/kg bodyweight (bw ); water intake, 91 mL/kg bw). 2. By CSNS, mean arterial blood pressur e (MAP) was lowered for periods of 20 min to levels between 101 +/- 4 and 56 +/- 5 mmHg. 3. In another group of conscious dogs, renal perfus ion pressure (RPP) was lowered to 95 +/- 4 mmHg for periods of 20 min by partial suprarenal aortic occlusion in order to assess the influenc e of a reduced RPP on plasma renin activity (PRA) without concomitant CSNS. 4. During CSNS, PRA increased markedly (>100%) only when MAP was reduced below 75 mmHg. 5. With aortic constriction and an RPP of 95 m mHg, the increase in PRA was 955%, which is more than three-fold highe r than the increase in PRA during CSNS at MAP levels <65 mmHg (314%). 6. The observed responses indirectly support the hypothesis that basal activity in efferent renal nerve discharge is present even at rest an d can be inhibited by CSNS, and furthermore suggests that CSNS attenua ted the pressure-dependent renin release.