Innervation of brain intraparenchymal vessels in subhuman primates: ultrastructural observations

Sympathetic innervation of intraparenchymal blood vessels in the basal ganglia was demonstrated by transmission electron microscopy in arteries, arterioles, and capillaries of the subhuman primate brain. Small arteries (40-120 micron) and some arterioles (12-40 micron) are innervated only at branching sites. However, arterioles occasionally may be innervated at points distal to their origin. Capillary innervation was very infrequently observed.