The protective effect of hypothermia on the recovery of neural activity after deprivation of oxygen and glucose: study of slices from the hippocampus and superior colliculus.

The effect of hypothermia on the tolerance of the cortex and brain stem to anoxic insult was investigated using slices from the hippocampus and superior colliculus of the guinea pig. The postsynaptic potential (population spikes) was recorded in the granule cell layer of the hippocampal slices after electrical stimulation to the perforant path. In the case of the superior collicular slices, the postsynaptic field potential was recorded in the superficial gray layer (SG) after stimulation to optic layer (OL). Perfusion medium deprived of oxygen and glucose completely blocked the electrical activity which subsequently recovered after reintroduction of oxygen and glucose. Monitoring the electrical activity, we studied the effect of temperature (37 degrees C, 35 degrees C, 33 degrees C and 30 degrees C) during deprivation of oxygen and glucose on the survival time of each slice. With mild hypothermia (35 degrees C) the survival time of slices from the superior colliculus was 15 min whereas that of hippocampal slices was 10 min. At 33 degrees C and 30 degrees C the hypothermia had a similar protective effect on the survival time in both slices from hippocampus and superior colliculus. These results suggest that there is a regional difference in the resistance of brain tissue to anoxia, and the brain stem is more resistant to anoxia than the cortex under mild hypothermic condition (35 degrees C).