Pattern and innervation of pial microvascular effectors which control blood supply to cerebral cortex.

In experiments with adult rabbits the active microvascular segments located at particular sites of the minor pial arterial ramifications were investigated. These appeared as sphincters at off-shoots of the arterial branches, the precortical arteries, and the arterial microanastomoses. The sphincters and the precortical arteries were found plentifully supplied with the cholinergic and adrenergic nerves, but the innervation of the microanastomoses was not considerably different from that of the adjacent arterial branches. The nerves of the precortical arteries were in direct connection with the nerve fibers of the arterial branches located inside the cerebral cortex. The pattern of distribution and innervation of the active vascular portions in pial microvascular bed suggests the probability of a neurogenic control of the blood supply to the smallest areas of the cerebral cortex.