Early life stress induced sex-specific deficits in social discrimination abilities and altered central vasopressin release

Abstract

Early life stress in humans is a risk factor for the development of psychopathologies. In rodents, maternal separation (MS; 3-h daily, day 1–14) is an established animal model of early life stress inducing increased anxiety and stress responsiveness in adulthood. However, the effects of maternal separation on social behaviors are mostly unknown. Therefore, we investigated whether MS affects social discrimination abilities in adult male and female Wistar rats. MS induced severe deficits in social memory during the social discrimination test in male, but not in female, rats. In contrast to control rats, male MS rats were unable to discriminate between a known and a novel juvenile rat 1h after re-exposure to the known juvenile. The total social investigation time was higher in males than in females independent of the treatment. A spatial memory test (y-maze) indicated that non-social memory abilities were not affected by MS. To understand possible underlying neurobiological mechanisms, we used intracerebral microdialysis to measure the local in vivo release of the neuropeptide vasopressin within the septum during the acquisition of social memory. We demonstrated that the social memory deficit of male MS rats was accompanied by a lack of an increase in vasopressin release within the medio-lateral septum, a brain region involved in social recognition. Alterations in vasopressin release in MS rats were social stimulus-specific as exposure to forced swimming induced a similar increase in septal vasopressin release in male control and MS rats. In conclusion, early life stress impairs social discrimination abilities and alterations in septal vasopressin release may underlie these behavioral changes. Supported by BMBF (IDN)