Ethanol effects on aggression of rats selected for different levels of aggressiveness.

Male rats confronting strange male intruders into their home cages were divided into nonaggressive, low-to-intermediate aggressive, and highly aggressive groups. In tests with low (0.3 and 0.6 g/kg) doses of ethanol the nonaggressive rats did not become aggressive; low-intermediate animals showed a significant increase in frequency and duration of attack behaviors; but highly aggressive rats displayed a slight (nonsignificant) decline. A higher ethanol dose (1.2 g/kg) consistently led to decreased aggression. This rate-dependency of the enhancement of aggression by low doses of ethanol is concordant with a view that the mechanism of this enhancement involves ethanol interference with some mechanism which normally acts to limit or inhibit attack.