Nitric oxide and the cerebral vascular function

The presence of a cholinergic vasodilator innervation to cerebral circulation is well established. Despite its high endogenous concentration in cerebral blood vessels, acetylcholine (ACh) is not the transmitter for vasodilation. This finding has led to the discovery that nitric oxide (NO), which is coreleased with ACh and neural peptides such as vasoactive intestinal polypeptide (VIP) from the respective cholinergic-nitrergic (nitric oxidergic) nerves and the VIPergic-nitrergic nerves, is the primary transmitter in relaxing smooth muscle. ACh and VIP act pre-synaptically to inhibit and facilitate, respectively, the release of NO. Release of NO from cerebral vascular endothelial cells is also well established. A similar system for recycling L-citrulline to L-arginine for synthesizing more NO has been demonstrated in both cerebral perivascular nerves and endothelial cells. Neuronal and endothelial NO appears to play an important role in con trolling cerebral vascular tone and circulation in health and disease. Copyright (C) 2000 National Science Council,ROC and S. Karger AG, Basel.