Effects of Hyperthermia on Neuronal Nitric Oxide Synthase Expression after Cerebral Ischemia in Gerbils

ABSTRACT

PURPOSE: This study was aimed to elucidate the effect of hyperthermia on neuronal nitric oxide synthase(nNOS) expression in both cerebral hemispheres after left common carotid artery occlusion in gerbils. METHODS: Using Mongolian gerbils, cerebral ischemia was produced by occluding carotid artery for 1-4 hours. Rectal temperature was maintained at 36degrees C for normothermia and 40degrees C for hyperthermia by heating pad. Western blot and RT-PCR was used to examine the nNOS and the mRNA expression. Neuronal damages were observed by histological study. RESULTS: After cerebral ischemia, mRNA of nNOS was expressed more abundantly in ischemic hemisphere than control in both normothermia and hyperthermia. Hyperthermia reduced nNOS protein expression markedly. In pathological study, neurons of hippocampal region were degenerated by ischemia. Hyperthermia by itself induced neuronal degeneration in both control and ischemic region. In immunohistochemistry of brain, there was no significant difference of nNOS expression between normothermia and hyperthermia. CONCLUSION: These findings suggest that increase in body temperature might enhance nNOS mRNA expression but reduce nNOS protein, and that hyperthermia aggravates neuronal damage by ischemia, independent of nNOS gene expression.