Sciatic nerve stimulation induces hypotension but not renal or lumbar sympathoinhibition in hypertensive Dahl rats.

Abstract

Sustained reductions in arterial pressure and sympathetic nerve activity occur after prolonged sciatic nerve stimulation in spontaneously hypertensive and pre-hypertensive Dahl salt-sensitive rats whereas these responses are not observed in renal hypertensive or Dahl resistant rats. These observations suggest that the development of post-stimulation hypotension and sympathoinhibition may be related to the genetic predisposition for hypertension rather than to the increased level of arterial pressure. However, it is not known whether the magnitude of the post-stimulation blood pressure and sympathetic nerve responses are influenced by the increased level of arterial pressure in addition to the genetic predisposition to hypertension. In the present study, we sought to determine if sustained sciatic nerve stimulation induces post-stimulation hypotension in hypertensive Dahl sensitive (DS) rats. For this purpose, mean arterial pressure (MAP), heart rate (HR), renal (RSNA) and lumbar (LSNA) sympathetic nerve activity were recorded during and after sciatic nerve stimulation in hypertensive DS rats (n = 17) fed an 8.0% NaCl diet for 7-8 weeks. Sciatic nerve stimulation increased HR (control, 443 +/- 10 b.p.m.; stimulation, 487 +/- 8 b.p.m.; p < 0.05) and tended to increase MAP, RSNA and LSNA. Two hours after stimulation, MAP was reduced (control 145 +/- 5 mmHg; recovery, 124 +/- 8 mmHg; p < 0.01) from control values. In contrast, RSNA and HR remained unchanged whereas LSNA was increased (69 +/- 20%; p < 0.05) from control values 120 min after stimulation. MAP, HR and RSNA were unchanged from control values during and for 2 h after sham stimulation in eight DS rats.(ABSTRACT TRUNCATED AT 250 WORDS)