Ethanol-induced depression of aggression in mice antagonized by hyperbaric exposure

The present study investigated the effect of hyperbaric exposure on ethanol-induced depression of aggressive behavior measured by resident-intruder confrontations. Adult male CFW mice (residents) were paired with females and housed together for 26 days. Then, resident mice were intubated with either ethanol (2 g/kg) or water (20 ml/kg) and were exposed to 1 atmosphere absolute (ATA) air, 1 ATA helium oxygen (heliox) or 12 ATA heliox using a within-subjects counterbalanced design. Thirty minutes after intubation an intruder was introduced. Ethanol significantly decreased aggressive behaviors (attack latency, attack bites, sideways threats, tail rattles and pursuit) in 1 ATA-treated animals. Pressure completely antagonized the depression of aggression induced by ethanol. Ethanol alone and pressure alone did not significantly affect nonaggressive behaviors. There were no statistically significant differences between groups in blood ethanol concentrations 50 minutes after intubation. These results suggest that ethanol's effects on aggressive behavior result from the same membrane actions leading to loss of righting reflex, depression of locomotor activity, tolerance and dependence.