Early emergence of altered 5-HT2A receptor-evoked behavior, neural activation and gene expression following maternal separation.

•Postnatal pups with a history of maternal separation exhibit enhanced 5-HT2A receptor-mediated head-twitch behavior.•Maternally separated pups exhibit reduced neural activation in the prefrontal cortex and lateral septum.•A history of maternal separation alters the pattern of 5-HT2A receptor activation evoked immediate early gene expression in the prefrontal cortex.