The effect of intraischemic mild hypothermia on focal cerebral ischemia/reperfusion injury.

The protective role of intraischemic mild hypothermia on brain injury associated with cerebral ischemia/reperfusion was investigated using a localized, no-flow cerebral ischemia/reperfusion model in rats in vivo.Male Wistar rats weighing 250-350 g were anesthetized lightly with halothane. All rats were randomly allocated into two series experiments the first of which was for study of infarct volume and the second of which was for study of NO (nitric oxide) content, and then subjected to various time intervals of focal ischemia followed by reperfusion. The intraischemic mild hypothermia was induced by feedback-regulated semiconductor cooling block in a group of these rats. Normothermia groups were considered as the control groups. The infarct volume and the NO content of rat brain were measured in different groups and hours respectively.The infarct volume of mild hypothermia group was significantly different from that of normal control group within the time window of 10 min (P < 0.05), infarcted brain volumes in hypothermic rats were significantly smaller than in normothermic rats, for the time window of 1 h there was no significant difference in the infarct volume between mild hypothermic group and normothermic control group (P > 0.5). Furthermore, increased tissue levels of NO, a potential mediator of cerebral injury in the brain following focal ischemia were depressed by mild hypothermia.It is suggested that localized mild hypothermia may be a protective against focal cerebral ischemia/reperfusion injury and that the decreased nitric oxide production in the brain may serve as the protective mechanism of hypothermia.