Ethanol-induced enhancement of defensive behavior in different models of murine aggression.

The effects of alcohol on agonistic behavior in mice were studied by introducing an intruder mouse to a resident, alcohol-treated test animal (or saline-injected control). Alcohol (0.1-2.0 g/kg, IP) was administered 20 minutes before testing, and an ethological analysis was made of all behavioral elements shown by the treated animal during a 500-second period. Alcohol did not increase aggression, whether baselines were high, low or experimentally suppressed. Defensive activities, however, were dose-dependently increased, with a threshold dose of 0.5 g/kg or lower in some situations. This suggests that alcohol did not reduce "anxiety" or "fear." Aggression tended to decrease, even with doses as low as 0.5 g/kg, which produced BACs of only 25-40 mg/dl at the start of the testing period. With the highest dose, however, aspects of timidity were still increased after 3 hours, but aggression returned to control level after 1 hour, when the BAC was about 250 mg/dl. In other studies, increased aggression has generally been found only with low alcohol doses. This acute tolerance to the anti-aggressive effect of alcohol reported here suggests the possibility of finding pro-aggressive effects at much higher BACs, perhaps more closely simulating the human situation.