The effects of acute and chronic alcohol ingestion on outcome following multiple episodes of mild traumatic brain injury in rats

Objective: Recent studies suggest that in some circumstances, alcohol intox ication at the time of severe head injury may be neuroprotective. The objec tive of this study was to determine the effect of acute and chronic alcohol ingestion on outcome in rodents sustaining multiple episodes of mild traum atic brain injury while intoxicated. Methods: For two weeks before experime ntation, adult male Sprague-Dawley rats received intoxicating levels of 95% ethanol (3 g/kg) or normal saline (NS) every other day by orogastric insti llation. On the day of experimentation, the animals were randomized to rece ive alcohol or NS. Two hours later, the animals received either mild (1.2 /- 0.4 ATA) fluid percussion injury (FPI) or no injury. The injured animals received a total of three episodes of FPI (once every four days). Mean ref lex recovery time (RRT) was determined (seconds +/- SEM) immediately after each episode. Mean latency time (seconds +/- SEM) for Morris Water Maze (MW M) performance was assessed at posttrauma days 11-19. Results: The chronic alcohol-exposed (CA) and the non-alcohol-exposed (NA) animals intoxicated w hen injured had prolonged escape, righting, and corneal RRTs after each FPI compared with the nonintoxicated injured animals and the noninjured shams. However, the CA animals had significantly shorter RRTs when compared with the NA rats. All the injured animals had MWM deficits on testing days 1-6 c ompared with the noninjured controls. On the last two MWM testing days, the injured NA animals had significantly better MWM performance than the injur ed CA rats. Conclusions: The injured intoxicated CA animals had a more rapi d recovery of reflexes compared with the injured intoxicated NA animals. De spite initial MWM deficits, the injured NA rodents eventually began to lear n the MWM. The injured CA rats never learned the maze. Under the conditions of this study, acute alcohol intoxication at the time of multiple episodes of minor head trauma did not provide neuroprotection for NA or CA rodents.