ObjectiveTo investigate the effects of Chaihu and Longgu Mulitang （CLMT） on hippocampal neural damage in the mouse model of depression via the extracellular signal-regulated protein kinase （ERK）/cAMP-response element-binding protein （CREB） signaling pathway.MethodsSeventy-eight male C57BL/6 mice were randomly allocated into normal control， model， low/medium/high-dose （2.89， 5.78， and 11.56 g·kg^-1， respectively） CLMT， and paroxetine （10 mg·kg^-1） groups. A depression model was established by chronic unpredictable mild stress （CUMS） combined with social isolation. Behavioral tests were carried out to evaluate depressive-like behaviors. Hematoxylin-eosin staining and Nissl staining were performed to assess hippocampal morphology and neuronal damage. Immunofluorescence was employed to detect glial fibrillary acidic protein （GFAP） and ionized calcium-binding adapter molecule 1 （Iba1）. Real-time PCR was employed to measure the mRNA levels of ERK and CREB. Western blot was employed to determine the expression of ERK/CREB pathway proteins and brain-derived neurotrophic factor （BDNF） in the hippocampal tissue. Molecular Operating Environment （MOE） software was used for molecular docking to evaluate the interactions between CLMT components and target proteins.ResultsCompared with the normal control group， the model group showed decreased sucrose preference （P0.01）， increased tail-suspension immobility time （P0.01）， decreased activity in the central region of the open field test （P0.01）， and decreased activity in the middle and open-arm region of the elevated plus maze test （P0.01）. The hippocampal area in the model group showed wrinkled cells and a reduction in the number of cells， neurons with reduced sizes and Nissl bodies， enhanced fluorescence intensity of GFAP and Iba1 （P0.01）， and down-regulated expression of phosphorylated （p）-ERK， p-CREB， and BDNF （P0.05， P0.01） and mRNA levels of ERK and CREB （P0.01）. Compared with the model group， the CLMT group showed increased body weight （P0.05， P0.01）， restored cell morphology， with only a small number of ruptured cells， normal neuronal structure and morphology with obvious nuclei and abundant Nissl bodies， weakened fluorescence intensity of GFAP and Iba1 （P0.05， P0.01）， up-regulated mRNA levels of ERK and CREB （P0.05， P0.01） and protein levels of phosphorylated （p）-ERK， p-CREB， and BDNF in the hippocampal tissue （P0.05， P0.01）. The results of molecular docking indicated that nine active ingredients in CLMT had good binding affinity with ERK and CREB.ConclusionCLMT may ameliorate the hippocampal nerve injury in the mouse model of depression by regulating the ERK/CREB pathway.

Chaihu and Longgu Mulitang;extracellular signal-regulated protein kinase（ERK）;cAMP-response element-binding protein （CREB）;chronic unpredictable mild stress （CUMS）;depression