ABSTRACT
Objective:To analyze the differences in neuronal activation during fear memory extinction in various sub-regions of the hippocampus in post-traumatic stress disorder(PTSD)mice.Methods:Two immediate early gene-pro-tein labeling strategies were employed to label neurons associated with fear extinction in PTSD mice.In the first group,Arc protein in hippocampal neurons was labeled and observed through immunofluorescence staining in wild-type mice.In the second group,Fos-CreERT2;Ai9 transgenic mice were injected with tamoxifen 23 hours prior to inducing fear memory extinction,and the relevant neurons were labeled with fluorescent proteins for observation.The number of labeled hippocampal neurons and the dendritic branch structure were analyzed to compare the activation levels of hipp-ocampal neurons and the plasticity of neuronal dendrites.Results:The two groups of Arc and Fos positive neurons were mainly distributed in the dorsal hippocampus,in which Arc protein chromogenic was enriched in CA3 and DG subre-gions,while CA1 and CA2 subregions were scattered,while Fos-positive neurons were enriched in the DG subregion of hippocampus and scattered in CA1,CA2 and CA3 subregions.Compared to the control group,there was no significant difference in the number of neurons expressing Arc protein in each subregion of the hippocampus in the PTSD group.The number of Fos-positive neurons in CA1,CA3 and DG subregions in the hippocampus of the PTSD group was signifi-cantly increased(P＜0.01).The dendritic branches of neurons in the hippocampal region were observed and analyzed in Fos-CreERT2;Ai9 mice from both groups,but no significant changes were found.Conclusion:Abnormal activation of neurons occurs in different subregions of the hippocampus during fear extinction in PTSD mice,although there are no significant plasticity changes in the dendritic branches of the activated neurons.