Sympathetic nerve responses to sustained stimulation of somatic afferents in Dahl rats

We tested the hypothesis that the hypotensive and sympathoinhibitory responses which occur after somatic afferent stimulation would be augmented in prehypertensive rats genetically predisposed to hypertension (Dahl salt-sensitive, DS) compared with rats resistant to the development of hypertension (Dahl salt-resistant, DR). For this purpose, we recorded mean arterial pressure (MAP), heart rate and renal sympathetic nerve activity (RSNA) during and following 30-min sciatic nerve stimulation in DS and DR rats fed a 0.4% NaCl diet. Baseline MAP did not differ significantly in the DS and DR rats. Somatic afferent stimulation in DS rats increased (P less than 0.05) MAP and heart rate and tended to increase RSNA whereas, in DR rats, stimulation increased (P less than 0.05) heart rate and tended to increase RSNA and MAP. Following somatic afferent stimulation, there were significant reductions (P less than 0.05) in both MAP (-20 +/- 6 mmHg) and RSNA (-36 +/- 8%) in DS rats. In contrast, DR rats did not exhibit significant poststimulation changes in MAP, and RSNA remained elevated from control following somatic afferent stimulation. These results suggest that the poststimulation inhibition of RSNA in DS rats may be related to the genetic predisposition of these rats to develop hypertension.