Spontaneous temperature changes in the 2-vessel occlusion model of cerebral ischemia in rats.

Transient global ischemia (ISC) in rats and humans causes selective and delayed neuronal death in the hippocampal CA1 sector. It is clear from rodent studies that hyperthermia aggravates, whereas hypothermia lessens, this injury. In this study we sought to relate core (Tc) and brain (Tb) temperature, measured via telemetry probes, after ISC produced in rats by bilateral common carotid artery occlusion combined with systemic hypotension (2-VO model). We also tested whether spontaneous postischemic temperature fluctuations occurred and whether they were related to cell death as previous studies indicate. We report that Tc and Tb readings are similar and are highly correlated before and after 10 min of 2-VO ISC. In the second experiment, rats were subjected to 8, 9, or 10 min of 2-VO ISC. Despite a range in CA1 injury among these animals, there was no evidence of post-ISC hyperthermia, contrary to earlier work, and neither temperature nor the physiological variables measured during ISC (e.g., glucose) predicted injury. Our findings suggest that, under the present conditions, 2-VO rats do not experience postoperative hyperthermia, which can be adequately measured with Tc telemetry probes.