Regulation ofBlood-Brain Barrier Endothelial Cells byNitric Oxide

Abstract Nitric oxide (NO)synthesized byvascular endo- thelial cells isapotent vasodilator substance. Theactions of NO extend wellbeyond itsvasodilatory properties, andin- creasingly, NO hasbeenrecognized asanimportant signal for intercellular andintracellular communication. Recently, NO hasbeenimplicated intheregulation ofvascular andblood- brain barrier permeability. NO hasalso beenshowntomod- ulate ionchannels inexcitable cells, thusaffecting neuronal firing. We report theresults ofpatch-clamp experiments that showamodulatory action ofNO aswellascGMPandcAMP onahyperpolarization-activated current (Iha) carried byboth