Action of psychoactive drugs on sex-related differences of OF1 mice; intraspecific aggressiveness and acute hypoxia survival.

The purpose of this study was to examine (1) whether there were a relationship between the sex-related differences in 51-day-old OF1 mice, regarding male aggressiveness and their sensitivity to an acute hypoxic (nitrogen) 50% lethal challenge, and (2) whether these sex-related differences could be modified by psychoactive drugs acutely injected at nonincapacitating doses. The introduction of a previously isolated male in grouped (10) mice decreased survival to the hypoxic challenge more in females than in males. The previously isolated male, which acted as an 'aggressor' with grouped mice (fights and flights in male groups, and mounts in female groups), had a higher hypoxic mortality than the mice of the groups under aggression. Psychoactive drugs were intraperitoneally injected in grouped mice before the introduction of the male aggressor. Clorazepate (5 and 25 mg/kg) abolished the sex-related difference in hypoxic survival in groups in the presence of, but not in the absence of, the previously isolated male. Conversely, hydroxyzine (5 mg/kg) and dexamphetamine (1 mg/kg) suppressed the sex-related difference only in the absence of the aggressor. The effects of these drugs appeared to be associated more with flight than with fight reactions provoked by the introduction of the male aggressor. A deep hypothermia was noted in clorazepate-treated mice at the issue of the hypoxic challenge.