Central dual innervation of arterioles and capillaries in the brain.

Fluorescence-and electron-microscopic studies were performed on nerve terminals close to intracerebral blood vessels in the rat. For the electron microscope subdural perfusion fixation with potassium permanganate was used. In the rat cerebral cortex deprived of the bilateral superior cervical ganglion some aminergic terminal boutons containing large and small core vesicles were observed contiguous to blood vessels. These terminals abutted on the capillary basement membrane. Since these terminals are found in the rat after bilateral superior cervical ganglion exision, they probably originate from central catecholaminergic neurons in the brain stem. These findings suggest that central aminergic neurons might play some role in cerebral blood flow regulation. In addition to aminergic terminal boutons, non-aminergic nerve terminals containing non-core vesicles also ended in the capillaries. Cerebral capillaries also have central dual innervation, aminergic and cholinergic, and dual peripheral innervation by sympathetic and parasympathetic fibers.