Regional cerebral blood flow autoregulation in normotensive and spontaneously hypertensive rats — effects of sympathetic denervation

Abstract

The present study was designed to investigate the effect of acute sympathetic denervation on the regional cerebral blood flow (CBF) autoregulation during acute elevation of blood pressure in spontaneously hypertensive rats (SHR) and normotensive Wistar Kyoto rats (WKY). CBF to the parietal cortex and thalamus was measured by the hydrogen clearance method and, to test autoregulation, systemic arterial blood pressure was elevated by intravenous infusion of phenylephrine. Superior cervical ganglia were removed on both sides to interrupt sympathetic innervation in the deeper structures of the brain. Acute bilateral sympathetic denervation did not alter the resting blood pressure or CBF in either SHR or WKY. In innervated SHR, resting mean arterial pressure (MAP) was 165 ± 5 mm Hg (mean ± SEM) and the upper limit of autoregulation in the cortex was 210 ± 3 mm Hg, which was significantly lower than that in the thalamus (229 ± 3 mm Hg, p < 0.02). In bilaterally denervated SHR, the upper limits were lowered to 193 ± 4 mm Hg in the cortex (p < 0.02 vs. innervated SHR) and to 207 ± 5 mm Hg in the thalamus (p < 0.02 vs. innervated). In WKY, resting MAP was approximately 55 mm Hg lower than that in SHR. Acute denervation reduced the upper limits from 142 ± 3 mm Hg to 130 ± 4 in the cortex (p < 0.05) and from 158 ± 4 to 145 ± 4 in the thalamus (p < 0.05). These results indicate in either SHR or WKY that vasoconstrictive responses to an increase in blood pressure are greater in the thalamus than in the cortex and that acute interruption of sympathetic nerves alters the autoregulatory function of cerebral vessels in the cortex and thalamus as well. © 1986 American Heart Association, Inc.