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

► We examine the effect of changing the [K +] o and [Mg 2+] o in intracerebral arterioles. ► The low [K +] o in the cerebral penetrating arterioles produce a biphasic response. ► Biphasic response consists of transient constriction followed by dilation. ► The low [Mg 2+] o induces constriction, whereas the high [Mg 2+] o induces dilation. ► The low [K +] o may lead membrane depolarization induced by inactivity in Na +–K +–ATPase. We investigated the effects of changing the extracellular potassium as well as magnesium concentration ([K +] o and [Mg 2+] o) in cerebral penetrating arterioles. The internal diameter of isolated pressurized cerebral penetrating arterioles in rat was measured under the microscope in the low [K +] o, low [Mg 2+] o and high [Mg 2+] o, respectively. Vascular responses induced by the low [K +] o were observed in the absence and presence of several inhibitors. The low [K +] o 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+] o significantly induced constriction, whereas the high [Mg 2+] o induced dilation. We analyzed that transient constriction in the low [K +] o may be led by membrane depolarization induced by inactivity in Na +–K +–ATPase. The vasomotor responses of the changing of [K +] o as well as [Mg 2+] o in a cerebral microcirculation may influence the pathological and therapeutic condition in cerebrovascular diseases, and may provide new therapeutic targets.