Effect of ethanol on aggression and timidity in mice

Abstract

The effects of ethanol (0.4, 0.8, 1.6, and 2.4 g/kg p.o.) on behavior of aggressive, timid, and sociable male mice treated with the drug on paired interactions with non-aggressive males given water were investigated. Under control interactions, aggressive mice attacked their partners, timid mice showed defensive-escape activities though their partners were completely non-aggressive, and sociable mice intensively investigated their partners. A low dose of ethanol (0.4 g/kg) increased while higher doses (0.8 to 2.4 g/kg) reduced aggressive activities in aggressive mice. Ethanol (0.8 g/kg) also evoked aggressive behavior in non-aggressive timid mice but no dose of ethanol stimulated aggression in non-aggressive sociable mice. Ethanol altered timid defensive-escape activities only in the highest dose of 2.4 g/kg: this dose increased defences and escapes in aggressive males while it reduced defensive upright postures in timid mice. However, 2.4 g/kg of ethanol reduced also another upright movement (exploratory rearing) in timid mice. Sociable activities were not increased by any dose of ethanol tested. By contrast, 0.4 g/kg of ethanol reduced sniffing and following partners in sociable mice. Thus, ethanol exhibit relatively strong aggression-stimulating effects in aversively disposed subjects while the drug was not able to supress timid defensive escape behavior and to stimulate active non-aggressive contacts between strange male mice.