[Differences in the effects of naltrexone on the communicative and aggressive behaviors of subjects with different experiences of social conquests].

The authors studied the effect of naltrexone (0.25 and 1.0 mg/kg, intraperitoneal injection) on the communicative and aggressive behavior of male C57BL/6J mice with experience in triumphs in 20 tests (victors) and of mice without such experience (novices). The level of communicativeness and aggression at the first confrontation was more marked in novices than in victors. In the novices 0.25 mg/kg naltrexone selectively reduced communicativeness and in a dose of 1.0 mg/kg shortened the sum time of the aggressive attacks, increasing in this case the time of aggressive grooming. In the victors naltrexone in both doses had no effect on the communicative behavior and period of aggressive grooming but increased the duration of the attacks depending on the dose. In both groups naltrexone increased the number of subjects which demonstrated aggressive attacks and reduced the frequency of aggressive grooming. It is concluded that the state of opiate receptors changes under the effect of repeated experience in the triumph of social confrontations.