Endogenous hippocampal estrogen is involved in stress-induced depression-like behaviors and spine plasticity in male rats

•Letrozole infusion into hippocampys induces depression-like behaviors in control rats.•E2 treatment alleviates depression-like behaviours induced by CUMS or letrozole infusion.•Neural E2 regulated the spine density in hippocampus.•Kalirin-7 is involved in this regulation of nE2 on spine density in hippocampus.