Previous studies have shown that elevating the K + levels from 0.75% to 2.11% in the diet of stroke-prone spontaneously hypertensive rats significantly retards the development of stroke and increases their lifespan. On the other hand, stroke-resistant spontaneously hypertensive rats fail to develop stroke even if they are fed the low-K + version of this diet Since sympathetic nerves surrounding the cerebral vasculature play an important role in protecting the brain from stroke during hypertension, I studied whether changes in sympathetic nerve density accounted for the differing incidences of stroke in stroke-prone spontaneously hypertensive rats fed high-and low-K + diets and in stroke-resistant and stroke-prone spontaneously hypertensive rats fed a low-K + diet At 14 weeks of age, all 11 stroke-prone rats fed the low-K + diet had evidence of cerebral hemorrhage while such lesions were virtually absent in the 11 littennates fed the high-K + diet and totally absent in the eight stroke-resistant rats fed the low-K + diet Stroke-prone (regardless of diet) but not stroke-resistant rats exhibited greater sympathetic nerve densities in the left hemisphere than in the right When stroke-prone rats were compared, in some areas of the cerebrovasculature, rats fed the high-K + diet had greater mean sympathetic nerve densities than those fed the low-K + diet On the other hand, stroke-resistant and stroke-prone rats fed the low-K + diet exhibited comparable sympathetic nerve densities in most cerebral arteries studied. I conclude that the small increases in cerebrovascular sympathetic nerve density observed in stroke-prone spontaneously hypertensive rats fed the high-K + diet would be of minor benefit in retarding stroke development Moreover, differences in sympathetic nerve density could not account for the different incidences of stroke observed between stroke-prone and stroke-resistant spontaneously hypertensive rats. (Stroke 1990;21:785-789) S ympathetic innervation plays an important role in protecting the cerebral vasculature from stroke during hypertension. Unilateral superior cervical sympathetic ganglionectomy in WistarKyoto stroke-prone spontaneously hypertensive rats (SPSHR) selectively denervates the cerebral arteries of one brain hemisphere. When done at weaning, such a procedure increases the incidence of stroke by 62.5%, with most strokes occurring in the denervated hemisphere.
12Various mechanisms by which sympathetic nerves protect the cerebral blood vessels have been proposed. Studies have demonstrated that sympathetic nerves exert a trophic influence on cerebral