Maternal separation during a specific postnatal time window prevents reinforcement of hippocampal long-term potentiation in adolescent rats

In an attempt to develop an animal model to study the etiology of brain dysfunction in relation to early life experience, we tested the hypothesis that early-life stress during specific postnatal time windows affects long-term potentiation (LTP) reinforcement in adolescence. Male Wistar rat pups were stressed by separation from their dams for 24 h at postnatal day (PND) 4, 9, or 18. The animals were tested for reinforcement of LTP at adolescence (9 weeks old) by exposing them to a 2-min swim-stress. Here, we show that maternal separation during (at PND9) but not at the beginning (at PND4) or after (at PND18) the stress-hyporesponsive-period of the hypothalamic-pituitary-adrenal-axis impairs emotional LTP-reinforcement in adolescent animals. Thus, this in vivo model allows the investigation of physiological and pathophysiological emotional information processing at the cellular level in freely behaving adolescent animals.