Material and Methods: 46 adult, male Sprague-Dawley rats were assigned to three homogenous groups by stratified random sampling according to their basal performance during the first four days of the Morris water maze (MWM), as Control (n=10), Sham (n=10) and Concussion (n=26) groups. On the 12th day, the MWM experiment was repeated to evaluate the memory function. Rats in the concussion group were then subjected to the first head trauma. Some of the trauma-applied rats were sacrificed for histopathological examination 4 hours (n=4) and 24 hours (n=3) after the trauma. The spatial memory function of the rest of the rats was re-evaluated by MWM on the 20th day. Some of the rats were then subjected to the second head trauma (n=13), four of which were then sacrificed at the 4th hour, and three of which were sacrificed at the 24th hour. On the 27th day, six rats that had received single concussion and the remaining six that had received two concussions were re-evaluated for retention development by the third MWM experiment.

Results: Escape latency curves showed a decrease in Sham and Control groups on the 20th and 27th days, and an increase in concussion group on the 20th day but no statistical significance was found between the groups.

Conclusion: Repetitious concussions did not significantly affect spatial learning-memory functions in rats, and may lead to a counter-adaptive mechanism against concussive injury. Keywords : Repetitious concussion, Head trauma, Concussion