ABSTRACT
<p><b>OBJECTIVE</b>To investigate the time course of calpain activity changes in rat neurons following fluid percussion injury (FPI) under normothermia (37 degrees celsius;) and mild hypothermia (32-/+0.5) degrees celsius;.</p><p><b>METHODS</b>In vitro cultured rat neurons were subjected to FPI followed by application of mild hypothermia for intervention at different time points, and the changes in intraneuronal calpain activity following FPI and the interventional effect of mild hypothermia on calpain activity were evaluated by UV-spectrophotometry at different time points.</p><p><b>RESULTS</b>Remarkable changes occurred in calpain activity in the neurons following FPI at 37 degrees celsius;, and mild hypothermia produced obvious interventional effect on calpain activity in close relation to the timing of intervention initiation.</p><p><b>CONCLUSION</b>Intraneuronal calpain activity changes following FPI are involved in the pathological process of cellular injury, and mild hypothermia might offer protection against traumatic brain injury to some extent by regulating calpain activity. The interventional effect of mild hypothermia is associated with the timing of the intervention initiation.</p>