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+]o and [Mg2+]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 [Mg2+]o and high [Mg2+]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 Ca2+ channel inhibitor but not by all K+ channel inhibitors. The low [Mg2+]o significantly induced constriction, whereas the high [Mg2+]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 [Mg2+]o in a cerebral microcirculation may influence the pathological and therapeutic condition in cerebrovascular diseases, and may provide new therapeutic targets.

Research highlights
► We examine the effect of changing the [K+]o and [Mg2+]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 [Mg2+]o induces constriction, whereas the high [Mg2+]o induces dilation.
► The low [K+]o may lead membrane depolarization induced by inactivity in Na+–K+–ATPase.