Effects of chronic mild stress induced depression on synaptic plasticity in mouse hippocampus

•Chronic mild stress induced depression-like behaviors and impaired spatial memory in adult mice.•Chronic mild stress induced the abnormal expression of TPH2 and TH in mouse hippocampus, cortex and midbrain.•Chronic mild stress decreased the quantity of astrocytes and increased the quantity of microglia in mouse hippocampus.•Chronic mild stress increased the density of synapse and small spine in inner and outer molecular layers of dentate gyrus. Chronic mild stress (CMS) model is most similar to the depression human suffered in daily life. Strong evidence proved the important role of hippocampal synaptic plasticity in the mechanism of depression. This study investigated the effect of CMS on synaptic plasticity in hippocampus. Our results showed that CMS impaired spatial memory and exploring ability, disturbed the release of neurotransmitters including 5-hydroxytryptamine (5-HT) and dopamine (DA), reduced the density of synaptic vesicle in inner molecular layer, increased the number of thin spines in inner and outer molecular layer, whereas did not affect the density of spine apparatus, the above mentioned were probably related to the reduction of astrocytes and activation of microglial cells.