Experiences Shape Hippocampal Neuron Morphology and the Balance of CRHR1 and OTR

Abstract The dorsal hippocampus (dHIP) is involved in avoidance behaviors regulation. It is unclear how experiences affect avoidance behaviors and the neuron morphology modulated by corticotrophin-releasing hormone (CRH) signaling and oxytocin receptor (OTR) system in the dHIP. We studied the effects of neonatal maternal deprivation (MD) and post-weaning environmental enrichment (EE) on the avoidance behaviors and neuron morphology of the dHIP in male BALB/c mice. We found that MD impaired avoidance memory, whereas EE improved that. MD increased Nissl bodies and neuronal complexity in the CA1 but decreased synaptic connections in the CA2–3 and DG. EE restored the Nissl bodies and neuron complexity alterations induced by MD in the CA1 and the synaptic connections alterations induced by MD in the CA3. MD increased CRHR1 levels in the CA1 and CA3 but decreased CRHR1 levels in the CA2. The effects of EE on the CRHR1 levels depend on whether MD or not. For MD mice, the EE treatment decreased CRH levels of the CA1–3 but only reduced the CRHR1 level of the CA3 region. MD probably increased OTR levels in the CA1, and EE could restore. Our study illustrates how MD and EE affect avoidance behaviors, hippocampal neuron morphology, and the OTR-CRHR1 balance. The results show that the alterations in dHIP’s regions induced by early life stress are partially restored by the late-life environmental improvement.