Effect of chronic sympathetic denervation on cerebrovascular hypertrophy during the development of hypertension in rats

Abstract

The present study was designed to examine the trophic effect of sympathetic nerves on cerebrovascular hypertrophy in developmental hypertension. Unilateral superior cervical ganglionectomy was performed in spontaneously hypertensive rats at 4 weeks of age, and wall-to-lumen ratios of cerebral arteries were determined at 5 weeks, 2 months or 5 months after denervation. To estimate the thickness of the vessel wall, a freeze substitution technique was used for the preparation of cerebral arteries. Basal mean arterial blood pressure measured through cannulated femoral artery was127 ±2, 2, 46 ± 7and168 ± 6mm Hg(mean±S.E.M.) at 9 weeks, 3 months and 6 months of age, respectively. The wall-to-lumen ratios in the denervated and innervated hemispheres were 0.124 ± 0.004and0.129 ± 0.005 at 9 weeks, 0.127 ± 0.003and0.169 ± 0.004 (P < 0.02vs denervated) at 3 months, and 0.194 ± 0.007and0.222 ± 0.006 (P < 0.05vs denervated) at 6 months. The effect of denervation was more significant in downstream vessels (diameter⩽ 100 μm) than larger ones. We conclude that wall-to-lumen ratio is correlated well with a rise in basal blood pressure, and chronic interruption of the sympathetic nerves attenuates normal occurrence of vascular hypertrophy during the development of hypertension.