Sympathetic inhibition after surgical reversal of renovascular hypertension in rats. Role of vagal nerves.

Abstract

The present study was undertaken to study the changes in efferent renal sympathetic nerve activity (RSNA) and heart rate (HR) during the acute fall in blood pressure after surgical reversal of two-kidney, one-clip renovascular hypertension in rats, and to explore if cardiopulmonary vagal afferents can influence sympathetic outflow in this situation. In 14 rats with a MAP of 199 +/- 6 mmHg the renal artery clip was surgically removed and after 90 min MAP had decreased to 109 +/- 7 mmHg. The HR had then decreased by 26 +/- 15 beats min-1 (P less than 0.05) and RSNA did not increase as expected, but was somewhat reduced (84 +/- 8% of control). In contrast, lowering pressure with nitroprusside to the same extent produced large and significant increases in HR and RSNA in seven other renal hypertensive rats. Acute bilateral vagotomy was performed in seven of the declipped rats, which induced an immediate increase in MAP (+35 +/- 10 mmHg, P less than 0.05), HR +28 +/- 10 beats min-1, P less than 0.05) and RSNA (+51 +/- 19%, P less than 0.05). A few minutes afterwards the vagotomy pressure again started to fall and was, after another 90 min 107 +/- 10 mmHg together with slight reductions in HR and RSNA. Another group of six rats were initially exposed to bilateral vagotomy. In these vagotomized rats declipping also induced hypotension (204 +/- 10 to 95 +/- 7 mmHg, P less than 0.001), together with tendencies of decreases in HR (425 +/- 17 to 397 +/- 17 beats min-1) and in RSNA (-4 +/- 6%).(ABSTRACT TRUNCATED AT 250 WORDS)