Neuroprotective effects of cromakalim on cerebral ischemia-reperfusion injury in rats--Correlation with hippocampal metabotropic glutamate receptor I alpha and glutamate transporter 1

摘要

BACKGROUND:Studies have reported that potassium channel openers exhibit a protective effect on cerebral ischemia-reperfusion injury and inhibit glutamate excitotoxicity in rats.However,the effects of the glutamate receptor 1α and glutamate transporter 1 remain poorly understood.OBJECTIVE:To investigate the prophylactic use of the adenosine triphosphate-sensitive potassium channel opener cromakalim on neurological function and cerebral infarct size,as well as glutamate receptor 1α and glutamate transporter 1 expression,in rats with cerebral ischemia-reperfusion injury,and to explore action mechanisms underlying reduced glutamate excitotoxicity and neuroprotection in rats.DESIGN,TIME AND SETTING:Randomized,controlled,animal experiment was performed at the Brain Institute,Qingdao University Medical College,Between July 2008 and April 2009.MATERIALS:Cromakalim was purchased from Sigma,USA;rabbit anti-glutamate receptor 1α polyclonal antibody was offered by Wuhan Boster,China;rabbit anti-glutamate transporter 1 polyclonal antibody was offered by Santa Cruz Biotechnology,USA.METHODS:Sixty male,Wistar rats,aged 6 months,were randomly assigned to three groups (n= 20):sham-surgery,model,and cromakalim.Intraluminal thread methods were used to establish middle cerebral artery occlusion in rats from the model and cromakalim groups.Rats from the sham-surgery group were subjected to exposed common carotid artery,external carotid artery,and internal carotid artery,without occlusion.Cromakalim (10 mg/kg) was administered 30 minutes prior to middle cerebral artery occlusion,but there was no intervention in the model and sham-surgery groups.MAIN OUTCOME MEASURES:At 24 hours post-surgery,neurological behavioral functions were evaluated using Bederson's test,cerebral infarction volume was determined following tetrazolium chloride staining,and glutamate receptor 1α and glutamate transporter 1 expressions were detected using immunohistochemistry.RESULTS:Following cerebral ischemia-reperfusion injury,neurological behavioral malfunctions were obvious in all mice.Focal cerebral infarction was detected in ischemic hemispheres,glutamate receptor 1α expression increased,and glutamate transporter 1 expression decreased in the ischemic hemisphere (P < 0.05).Compared with the model group,neurological behavioral functions significantly improved,cerebral infarction volume was significantly reduced (P < 0.05),glutamate receptor 1α expression was significantly decreased,and glutamate transporter 1 expression was increased in the cromakalim group (P < 0.05).CONCLUSION:Improved neurological function and reduced cerebral infarction volume in rats through the preventive use of cromakalim could be related to decreased glutamate receptor 1α expression and enhanced glutamate transporter 1 expression.