The severity of excitotoxic brain injury is dependent on brain temperature in immature rat

The effect of brain temperature on the severity of excitotoxic brain injury was evaluated in perinatal rats. Postnatal day (PND) 7 rats received unilateral intrastriatal injections of 25 nmol N-methyl-D-aspartate (NMDA) and then were exposed for 2 h to one of six different ambient temperatures. Animals were sacrificed 5 days later and the severity of brain injury was assessed quantitatively by comparison of the weights of the injected and contralateral cerebral hemispheres. Injection of NMDA consistently produced extensive unilateral brain injury in rats maintained at normothermia (36 degrees C ambient temperature; 29 +/- 1.8% reduction in the weight of the injected hemisphere). In the range of ambient temperatures between 25 degrees C and 40 degrees C, there was a linear relationship between temperature and the severity of NMDA-induced injury (r2 = 0.95, P less than 0.001, linear regression). In a separate analysis, in PND 7 rats, a positive linear relationship between ambient temperature (28 degrees C and 40 degrees C) and brain temperature was observed (r2 = 0.96, P less than 0.001). These data suggest that the severity of excitotoxic brain injury is dependent upon brain temperature.