An assessment of KIR channel function in human cerebral arteries

In the rodent cerebral circulation, inward rectifying K+ (K-IR) channels set resting tone and the distance over which electrical phenomena spread along the arterial wall. The present study sought to translate these observations into human cerebral arteries obtained from resected brain tissue. Computational modeling and a conduction assay first defined the impact of K-IR channels on electrical communication; patch-clamp electrophysiology, quantitative PCR, and immunohistochemistry then characterized K(IR)2.x channel expression/activity. In keeping with rodent observations, computer modeling highlighted that K-IR blockade should constrict cerebral arteries and attenuate electrical communication if functionally expressed. Surprisingly, Ba2+ (a K-IR channel inhibitor) had no effect on human cerebral arterial tone or intercellular conduction. In alignment with these observations, immunohistochemistry and patch-clamp electrophysiology revealed minimal K-IR channel expression/activity in both smooth muscle and endothelial cells. This absence may be reflective of chronic stress as dysphormic neurons, leukocyte infiltrate, and glial fibrillary acidic protein expression was notable in the epileptic cortex. In closing, K(IR)2.x channel expression is limited in human cerebral arteries from patients with epilepsy and thus has little impact on resting tone or the spread of vasomotor responses. NEW & NOTEWORTHY K(IR)2.x channels are expressed in rodent cerebral arterial smooth muscle and endothelial cells. As they are critical to setting membrane potential and the distance signals conduct, we sought to translate this work into humans. Surprisingly, K(IR)2.x channel activity/expression was limited in human cerebral arteries, a paucity tied to chronic brain stress in the epileptic cortex. Without substantive expression, K(IR)2.x channels were unable to govern arterial tone or conduction.