Increase in perivascular noradrenergic nerve density and decrease in acetylcholinesterase-positive sympathetic nerve density in the kidneys of spontaneously hypertensive rats.

The density and pattern of sympathetic nerve fibres in the kidneys of 16-week-old spontaneously hypertensive rats (SHR) and of control age-matched normotensive Wistar-Kyoto (WKY) rats were studied by catecholamine histofluorescence and acetylcholinesterase histochemical techniques. Varicose noradrenergic fibres primarily supply renal vasculature and were concentrated in small arteries and in afferent glomerular arterioles. The number and the density of these nerve fibres were increased in SHR. Acetylcholinesterase-positive nerve fibres were distributed to the renal vascular tree in the same way as the noradrenergic nerves and disappeared after chemical sympathectomy, suggesting their sympathetic nature. Acetylcholinesterase-positive perivascular nerve fibres were decreased in SHR. The possible significance of the two directional behaviour of sympathetic nerves (noradrenergic and acetylcholinesterase-positive) in the kidneys of SHR is discussed.