Thread occlusion but not electrocoagulation of the middle cerebral artery causes hypothalamic damage with subsequent hyperthermia.

Moderate changes in body temperature can influence the outcome of cerebral ischemic insults and the effect of drugs. Body temperature was measured continuously for 24 hours in rats subjected to permanent occlusion of the middle cerebral artery (MCA) by either coagulation or thread insertion, and the results correlated with the histology of the hypothalamus. The body temperature did not change after MCA occlusion by coagulation and the hypothalamus was intact in all rats. In contrast, the body temperature rapidly increased from about 38 degrees C to more than 39.5 degrees C after MCA occlusion using intraluminal thread, and hyperthermia continued for at least 6 hours in all rats. Histological evaluation revealed neuronal damage in the preoptic area of the hypothalamus in all rats undergoing thread occlusion. Long duration hyperthermia must be prevented after permanent MCA occlusion when the intraluminal thread occlusion model is used in chronic experiments.