Relationship between inward rectifier potassium current impairment and brain injury after cerebral ischemia/reperfusion.

Functional alterations of barium-sensitive potassium inward rectifier (KIR) current, which is involved in the vasodilation of middle cerebral arteries (MCA) in rat brain, have been described during brain ischemia/reperfusion (I/R). The authors investigate the effects of I/R on KIR current recorded in isolated myocytes from MCA of control rats and from contralateral and ipsilateral MCA of ischemic rats by the whole-cell patch-clamp technique, and the relationship between its alteration and the severity of brain injury. The vascular smooth muscle cells exhibited similar morphologic features in all conditions, and the KIR was present in the three groups of myocytes, exhibiting a characteristic inward rectification and a normal external potassium dependence. The KIR density was significantly reduced in cell of MCA ipsilateral to occlusion with a maximum at -135 mV, whereas there was no difference between control and contralateral cells. This alteration in KIR density in occluded MCA was significantly correlated with severity of brain injury and brain edema. These results suggest that the alteration of KIR density in MCA myocytes after I/R and the consecutive impaired dilation of MCA may contribute to aggravation of the brain injury.