Impacts of maternal separation stress on ethanol intake and endocannabinoid system in adolescent mice

•Maternal separation (MS) increased ethanol intake in a challenge-specific manner.•MS did not alter neuronal activation in response to an ethanol binge protocol.•MS affected ethanol preference in a concentration- and withdrawal-dependent way.•MS decreased dorsostriatal expression of Mgll gene – which encodes for MAGL enzyme.•MS did not change dorsostriatal expression of CB1- and FAAH-encoding genes. Clinical and preclinical studies suggest that early life stress can increase the risk of developing ethanol use disorder later in life. Although the endocannabinoid (eCB) system plays a role in stress-related behaviors and ethanol consumption, it remains unclear whether the eCB system is affected in response to a combination of both factors. By using male and female adolescent C57BL/6J mice subjected to a maternal separation (MS) stress paradigm from postnatal day (PND) 1 to 14, we explored (1) the consequences of early life stress experiences on ethanol consumption in adolescent mice and (2) how these events affect the eCB system and neuronal activation in brain regions associated with the reward system. In Experiment 1, we found that MS increased involuntary ethanol consumption specifically during the first exposure to the drug (during a 24 h-long trial on PND 28) and decreased the active/inactive nose poke ratio (discrimination index) specifically when mice were subjected to 1 h-sessions (PND 82–86) in an operant ethanol self-administration paradigm. In Experiment 2, during a two-bottle free choice paradigm, we found that MS increased mice preference for high ethanol concentrations (15 % and 20 %) but not lower ethanol concentrations (5 % and 10 %). Except for Mgll gene expression in the dorsal striatum (DS) in Experiment 2, no statistically significant effects of MS were observed regarding neuronal activation on the prefrontal cortex, DS, globus pallidus, and substantia nigra following a binge operant ethanol self-administration session (Experiment 1) or the eCB system molecules (Cnr1 and Faah gene expression) in the DS (Experiment 2).