Neuroprotective Effect of Diazoxide in Animal Model of Focal Cerebral Ischemia

Cheon, Young Hee; Suh, Byeong Hyun; Yoon, A Ram; Lee, Ji Hye; Woo, Ran Sook; Song, Dae Yong; Baik, Tai Kyoung

Abstract

Ischemic preconditioning is the earlier stress adaptive response that occurs during repeated episodes of the brief ischemia and reperfusion. It is now well known that this adaptive response can render the neuron more tolerant to the subsequent potential lethal ischemic injury. Although the selective mitochondrial K+ (ATP) channel opener induces protective effects similar to that of ischemic preconditioning, the underlying mechanism is not known yet. The purpose of this study was to investigate the mechanism of neuroprotective effect of diazoxide, a mitochondrial K+ (ATP) channel opener, pretreatment on a focal cerebral ischemic injury of rat brain. Thirthy-four Sprague-Dawley rats were used. Animals were randomly divided into normal control group, middle cerebral artery (MCA) permanent occulusion group (experimental control group), and diazoxide pretreated group. Animals were sacrified at 2 hours or 24 hours after MCA occulusion injury. For inducing the focal cerebral ischemic injury, the left MCA was occuluded by modified Longa's method. Diazoxide (3 mg/kg) was administrated through the femoral artery at 15 minutes earlier to surgical procedures. TTC-stained brain sections of experimental group showed a remarkable infarct injury in the ipsilateral cerebral cortex and striatum. However, the infarction volume of the diazoxide pretreated group was significantly reduced. Accordingly, the number of neurons undergoing eosinophilic degeneration and nuclear chromatin condensation was reduced by diazoxide pretreatment. TUNEL-positive neurons were not detected at 2 hours after MCA permanent occlusion but lots of them were observed at 24 hours. The number of c-fos immunoreactive neurons was remarkably increased at 2 hours following MCA permanent occulusion and reduced to the basal level at 24 hours in both experimental control and diazoxide pretreated group. However, the number of Bcl-2 or pAkt immunoreactivitive neurons of the diazoxide pretreated group outnumbered those of the experimental control group at all timepoints in our experiment. In conclusion, the pretreatment of diazoxide, K+ channel opener, could have europrotective effects on ischemic neurons by upregulating the expression of anti-apoptotic proteins, like Bcl-2 or pAkt.