Effects of binge ethanol administration on the behavioral outcome of rats after lateral fluid percussion brain injury

This study examined the effects of 4 weeks of binge ethanol administration (BEAn) on the behavioral outcome in rats after lateral fluid percussion (FP) brain injury. Rats were intragastrically given 7.5 mL/kg of either 40% ethanol in 5% glucose solution (3 g ethanol/kg; binge ethanol group), or 5% glucose solution (vehicle group), twice on Thursday and Friday of 3 consecutive weeks. Then rats from both groups were subjected to either lateral FP brain injury of moderate severity (1.8 atm) or to sham operation. Postinjury behavioral measurements revealed that brain injury caused significant spatial learning disability in both groups. There were no significant differences in mean search latencies in the sham animals between the vehicle and binge ethanol groups. On the other hand, the mean search latency of the binge ethanol group was significantly higher than that of the vehicle group in trial blocks 2 and 4. There were no significant differences in the target visits (expressed as mean zone difference [MZD]) during the probe trial between the injured animals of binge ethanol and vehicle groups. However, there was only a minor trend towards worsened MZD score in the binge-injured animals. Histologic analysis of injured animals from both injured ethanol and vehicle groups revealed similar extents of ipsilateral cortical and observable hippocampal damage. These results suggest that 4 weeks of binge ethanol treatment followed by ethanol intoxication at the time of injury worsens some aspects of the spatial learning ability of rats. This worsening is probably caused by subtle, undetectable morphologic damage by binge ethanol administration.