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

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Abstract
1. The interaction of electrical stimulation of the carotid sinus nerves (carotid sinus nerve stimulation, CSNS) with mechanisms of renin release was studied in conscious and unrestrained resting beagle dogs receiving a standardized diet (sodium intake, 4.5 mmol/kg bodyweight (bw); water intake, 91 mL/kg bw). 2. By CSNS, mean arterial blood pressure (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 perfusion pressure (RPP) was lowered to 95 +/- 4 mmHg for periods of 20 min by partial suprarenal aortic occlusion in order to assess the influence 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 mmHg, the increase in PRA was 955%, which is more than three-fold higher 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 and can be inhibited by CSNS, and furthermore suggests that CSNS attenuated the pressure-dependent renin release.