Long-term impairment of social memory in the rat after social defeat is not restored by desglycinamide-vasopressin.

Repeated social defeat followed by individual housing caused a long-term impairment of social memory in male rats. Social memory, as assessed in the social discrimination test using an intertrial interval of 3 min, was impaired for at least 8 weeks after the social defeat experience. Since social memory of male rodents depends on proper functioning of the sexually dimorphic vasopressin system, it was investigated whether a centrally active vasopressin fragment could restore the impaired social memory. Subcutaneous administration of 6 microg/kg of the vasopressin fragment desglycinamide-vasopressin (VP1-8) 40 days after social defeat slightly improved social memory in both control and socially defeated rats. It is concluded that social defeat followed by individual housing caused a long-term impairment of social memory, which was not restored by treatment with VP1-8.