Vasomotor response induced by change of extracellular potassium and magnesium in cerebral penetrating arterioles

We investigated the effects of changing the extracellular potassium as well as magnesium concentration ([K(+)](0) and [Mg(2+)](0)) in cerebral penetrating arterioles. The internal diameter of isolated pressurized cerebral penetrating arterioles in rat was measured under the microscope in the low [K(+)](0) low [Mg(2+)](0) and high [Mg(2+)](0), respectively. Vascular responses induced by the low [K(+)](0) were observed in the absence and presence of several inhibitors. The low [K(+)](0), produced a biphasic response consisting of an initial transient constriction followed by dilation. The transient constriction was attenuated by Na(+)-K(+)-adenosine triphosphatase (ATPase) inhibitor in a concentration-dependent manner and L-type Ca(2+) channel inhibitor but not by all K(+) channel inhibitors. The low [Mg(2+)](0) significantly induced constriction, whereas the high [Mg(2+)](0) induced dilation. We analyzed that transient constriction in the low [K(+)](0) may be led by membrane depolarization induced by inactivity in Na(+)-K(+)-ATPase. The vasomotor responses of the changing of [K(+)](0) as well as [Mg(2+)](0) in a cerebral microcirculation may influence the pathological and therapeutic condition in cerebrovascular diseases, and may provide new therapeutic targets. (C) 2011 Elsevier Ireland Ltd and the Japan Neuroscience Society. All rights reserved.