The Effect of Early Life Stress on Emotional Behaviors in GPR37KO Mice.

GPR37 is an orphan G-protein-coupled receptor, a substrate of parkin which is linked to Parkinson's disease (PD) and affective disorders. In this study, we sought to address the effects of early life stress (ELS) by employing the paradigm of limited nesting material on emotional behaviors in adult GPR37 knockout (KO) mice. Our results showed that, while there was an adverse effect of ELS on various domains of emotional behaviors in wild type (WT) mice in a sex specific manner (anxiety in females, depression and context-dependent fear memory in males), GPR37KO mice subjected to ELS exhibited less deteriorated emotional behaviors. GPR37KO female mice under ELS conditions displayed reduced anxiety compared to WT mice. This was paralleled by lower plasma corticosterone in GPR37KO females and a lower increase in P-T286-CaMKII by ELS in the amygdala. GPR37KO male mice, under ELS conditions, showed better retention of hippocampal-dependent emotional processing in the passive avoidance behavioral task. GPR37KO male mice showed increased immobility in the forced swim task and increased P-T286-CaMKII in the ventral hippocampus under baseline conditions. Taken together, our data showed overall long-term effects of ELS-deleterious or beneficial depending on the genotype, sex of the mice and the emotional context.