Autonomic innervation of cerebral blood vessels decreases in renal hypertensive rats.

The ultrastructural distribution of the autonomic nerves of brain arteries was investigated in renal (one-kidney, one clip) hypertensive and normotensive Wistar-Kyoto rats. Sympathetic and nonsympathetic nerve terminals were found only in the adventitial layer of brain arteries of renal hypertensive and normotensive rats. In both normotensive and renal hypertensive rats the total nerve endings were dense in anterior cerebral artery, moderately dense in middle cerebral artery, and sparse in basilar artery. In normotensive rats, nonsympathetic nerves outnumbered sympathetic nerves in anterior cerebral, middle cerebral, and basilar arteries. In renal hypertensive rats these two types of nerve terminals in close apposition to smooth muscle decreased in anterior cerebral and basilar arteries, while those in middle cerebral arteries remained unchanged. These results suggest that the potential neurogenic control of cerebral blood vessels as well as the trophic effect of sympathetic nerves on brain blood vessels may decrease in renal hypertensive rats. As this finding contrasts with that in spontaneously hypertensive rats, the pattern of innervation in brain arteries may differ in different types of hypertension.