Abstract
The present study was designed to investigate the cerebral blood flow (CBF) autoregulation and its relation to hypertrophy of arterial wall during development of hypertension in young spontaneously hypertensive rats. Unilateral superior cervical ganglionectomy was performed to examine the effects of sympathetic nerves on CBF regulation. Hydrogen clearance method was used to measure CBF and wall/lumen ratio was estimated with freeze-substitution technique.
Basal blood pressure were 88 mmHg at 4 weeks of age, 105 at 6 weeks and 127 at 9 weeks, and CBF were 51, 51 and 48 ml/100 g/min, respectively. The upper limits of CBF autoregulation were 109 mmHg, 126 and 168 in these rats, being correlated well with increase in basal blood pressure. In acutely denervated hemisphere, the upper limits were significantly lowered from 109 to 100 mmHg at 4 weeks and from 168 to 151 mmHg at 9 weeks. Chronic denervation (2 to 5 weeks after ganglionectomy) did not affect the autoregulatory range. The wall/lumen ratios of cerebral arteries were 0.133 at 4 weeks and 0.130 at 9 weeks, of which difference being not significant. Sympathetic denervation did not alter the ratio.
These results indicate that 1) upward shift of the CBF autoregulation with age is closely related to rise in basal blood pressure without evidence of increase in vascular hypertrophy, and 2) acute interruption of sympathetic nerves impairs the autoregulatory capacity during acute elevation of systemic blood pressure.
