NEW DEVELOPMENTS IN THE UNDERSTANDING OF CEREBRAL VASOREGULATION AND VASOSPASM - THE ENDOTHELIN NITRIC-OXIDE NETWORK

Endothelins, which are powerful vasoconstrictors, and nitric oxide, wh ich is a powerful vasodilator, together form a balanced system that re gulates blood flow in the brain and in other organs. Ongoing research may yield new drugs that act on this system to prevent or reverse cere bral vaso-spasm in subarachnoid hemorrhage and other conditions. KEY P OINTS Many compounds are involved in cerebral vasoregulation under phy siologic and pathologic conditions; of these, endothelins and nitric o xide have attracted considerable attention over the last several years . Endothelins and nitric oxide differ in chemical structure and pharma cological properties: endothelins are potent vasoconstrictor peptides consisting of 21 amino acids; nitric oxide is a free radical with a ha lf-life of only a few seconds and exerts powerful vasodilatory effects . Both are produced by a number of cell types in the brain and interac t at various levels to profoundly influence cerebral vessel function.