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NEUROHUMORAL CONTROL OF CARDIOVASCULAR FUNCTION

Afferent renal denervation impairs baroreflex control of efferent renal sympathetic nerve activity

¹Departments of Internal Medicine, ²Pharmacology, and ³Molecular Physiology and Biophysics, Department of Veterans Affairs Medical Center and University of Iowa Carver College of Medicine, Iowa City, Iowa

Submitted 23 June 2008 ; accepted in final form 20 October 2008

Increasing efferent renal sympathetic nerve activity (ERSNA) increases afferent renal nerve activity (ARNA), which decreases ERSNA to prevent sodium retention. High-sodium diet enhances ARNA, suggesting an important role for ARNA in suppressing ERSNA during excess sodium intake. Mean arterial pressure (MAP) is elevated in afferent renal denervated by dorsal rhizotomy (DRX) rats fed high-sodium diet. We examined whether the increased MAP in DRX is due to impaired arterial baroreflex function. In DRX and sham DRX rats fed high-sodium diet, arterial baroreflex function was determined in conscious rats by intravenous nitroprusside and phenylephrine or calculation of transfer function gain from arterial pressure to ERSNA (spontaneous baroreflex sensitivity). Increasing MAP did not suppress ERSNA to the same extent in DRX as in sham DRX, –60 ± 4 vs. –77 ± 6%. Maximum gain, –4.22 ± 0.45 vs. –6.04 ± 0.90% ERSNA/mmHg, and the maximum value of instantaneous gain, –4.19 ± 0.45 vs. –6.04 ± 0.81% ERSNA/mmHg, were less in DRX than in sham DRX. Likewise, transfer function gain was lower in DRX than in sham DRX, 3.9 ± 0.2 vs. 6.1 ± 0.5 NU/mmHg. Air jet stress produced greater increases in ERSNA in DRX than in sham DRX, 35,000 ± 4,900 vs. 20,900 ± 3,410%·s (area under the curve). Likewise, the ERSNA responses to thermal cutaneous stimulation were greater in DRX than in sham DRX. These studies suggest impaired arterial baroreflex suppression of ERSNA in DRX fed high-sodium diet. There were no differences in arterial baroreflex function in DRX and sham DRX fed normal-sodium diet. Impaired arterial baroreflex function contributes to increased ERSNA, which would eventually lead to sodium retention and increased MAP in DRX rats fed high-sodium diet.

dorsal rhizotomy; high-sodium diet; renorenal reflexes; spontaneous baroreflex sensitivity; reflex renal nerve stimulation

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				U. C. Kopp, O. Grisk, M. Z. Cicha, L. A. Smith, A. Steinbach, T. Schluter, N. Mahler, and T. Hokfelt Dietary sodium modulates the interaction between efferent renal sympathetic nerve activity and afferent renal nerve activity: role of endothelin Am J Physiol Regulatory Integrative Comp Physiol, August 1, 2009; 297(2): R337 - R351. [Abstract] [Full Text] [PDF]