Single episode of maternal deprivation and adult depressive profile in mice: interaction with cannabinoid exposure during adolescence.

Early life adverse experiences have been shown to increase the likelihood of developing later depressive symptoms. In this frame, human adolescents have been suggested to approach psychoactive drugs in order to self-medicate emerging depressive states. In keeping with these considerations, outbred CD-1 mice of both sexes, which underwent a single 24-h episode of maternal deprivation early in development, were administered the cannabinoid agonist WIN 55,212-2 (0, 0.5 or 2 mg/kg i.p.) during adolescence. Maternal deprivation reduced the expected interest in socio-sexual interaction with peers during adolescence. When mice were then tested at adulthood in the forced-swim paradigm in drug-free state, the latency to reach a passive floating posture was markedly reduced by early maternal deprivation. Low doses of cannabinoid (0.5 mg/kg) administered during adolescence were either able to reduce the time spent floating and to increase episodes of active struggling only in control non-deprived animals. As a whole, the emergence of depressive symptoms during both adolescence and adulthood seems to be eased as a consequence of a single/prolonged episode of early maternal deprivation early in infancy.