Vasopressin-induced suppression of renal sympathetic outflow depends on the number of baroafferent inputs in rabbits
Nishida, Y.; Bishop, V.S.
American Journal of Physiology 263(6 Pt 2): R1187-R1194
1992
ISSN/ISBN: 0002-9513 PMID: 1481926 Document Number: 388455
We tested the hypothesis that the inhibitory action of arginine vasopressin (AVP) on renal sympathetic nerve activity (RSNA) is related to the number of baroceptor stations. The role of baroreceptor afferents was determined by comparing the effects of AVP on the baroreflex function curves (mean arterial pressure (MAP) vs. %RSNA) obtained in intact conscious rabbits with those obtained in rabbits with one carotid sinus and one aortic nerve intact (1CSN + 1AoN) and in rabbits with only a single carotid sinus nerve intact (1CSN). Baroreflex curves were obtained by relating SIGMA-SNA to MAP during ramp increases and decreases in MAP. MAP was increased with phenylephrine and decrease with caval occlusion. In the intact state (n = 7), AVP infusions (0.4 1.5, and 3.0 mU cntdot kg-1 cntdot min-1) produced dose-dependent reduction in the maximum %RSNA (97 +- 1 to 85 +- 6, 68 +- 6, and 57 +- 5%, respectively) at minimum MAP and the gain of the baroreflex curve (5.7 +- 0.2 to 3.9 +- 0.2, 3.2 +- 0.3, and 2.2 +- 0.2 mm Hg, respectively) and shifted the midrange of the curves (72 +- 3 to 68 +- 4, 68 +- 2, and 63 +- 3 mmHg, respectively). However, in the 1CSN + AoN state (n = 6), the medium dose of AVP (1.5 mU cntdot kg-1 cntdot min-1) did not significantly alter the maximum SIGMA-SNA, the gain of the curve, or the midrange of the curve. The highest dose of AVP (3.0 mU cntdot kg-1 cntdot min-1) still reduced the maximum %RSNA (98 +- 3 to 75 +- 3) and the gain of the curve (4.1 +- 0.4 to 2.7 +- 0.2). In the 1CSN state (n = 8), even the highest dose did not significantly alter any parameter of the curve. These results demonstrated that AVP-induced suppression of the RSNA depends on the number of afferent inputs from baroreceptors.