CHOLINERGIC INNERVATION OF THE VASCULAR WALL

The wall of blood vessels involved in both peripheral and extracerebral circulations is innervated by parasympathetic cholinergic fibers. These fibers induce an endothelium-dependent relaxation which involves synthesis and release by endothelial cells of nitric oxide (NO), a diffusible agent acting as a muscular relaxant. Nerves capable of NO synthesis are present on extracerebral arteries and seem to release NO via a nicotinic-mediated pre-synaptic stimulation. In the cerebral cortex, intraparenchymal microvessels are in intimate relationship with cholinergic nerve terminals that are either intrinsic or that originate from the basal forebrain. This neurovascular apposition includes an intervening glial leaflet suggesting that astrocytes are involved in the regulatory mechanisms by which the brain controls its blood supply and the blood brain barrier. Thus, a neuronal-glial-vascular signalling mechanism is probably involved in the regulation of cortical microcirculation.