选择性过表达海马CB1R缓解慢性应激诱导的神经发生减弱及行为学损伤OA

Objective To investigate the effects of selective overexpression of hippocampal cannabinoid receptor 1(CB1R)on newly generated cells and newly matured neurons in the hippocampus of stress-induced rats.Methods Thirty-two 6-8 week-old male SD rats(body weight 180 to 220 g)were randomly assigned to a Control group(n=10)and a Stress group(n=22).After the Stress group underwent 3 weeks of chronic restraint stress(CRS),11 rats were randomly selected to form the Stress+CB1R-OE group,receiving hippocampal injections of an adeno-associated virus(AAV)for CB1R overexpression via stereotaxic surgery.The Control group and the remaining Stress group received a null AAV,designated as Control+AAV-NC and Stress+AAV-NC groups,respectively;viral transfection lasted 3 weeks.Body weight was measured every Sunday morning for weeks 1 to 7.Behavioral levels were assessed using the novel environment feeding suppression test.Immunofluorescence staining was used to detect the expression of 5-bromo-2'-deoxyuridine(BrdU),Neuronal Nuclei(NeuN),and CB1R in the hippocampal dentate gyrus(DG)(n=5 per group,3 slices per rat).A NOVEL confocal microscope was used for scanning.Imaris software calculated the density of BrdU+and BrdU+/NeuN+ cells per unit volume in the DG,while Image J software measured the mean fluorescence intensity of CB1R and NeuN in the DG.Western blot assay was used to detect hippocampal CB1R protein expression levels.Results After 3 weeks of CRS,the body weight of the Stress+AAV-NC group was significantly lower than that of the Control+AAV-NC group(P=0.001).Selective hippocampal CB1R overexpression for 3 weeks partially ameliorated body weight gain in the Stress+CB1R-OE group,but their weight remained significantly lower than the Control+AAV-NC group(P=0.004).The novel environment feeding suppression test showed that compared to the Control+AAV-NC group,the Stress+AAV-NC group had a significantly prolonged feeding latency(P＜0.001),with no significant difference in feeding amount within 5 min.After selective CB1R overexpression,the Stress+CB1R-OE group showed a significantly shortened feeding latency(P=0.039),with no significant differences in feeding amount among the three groups.Immunofluorescence results indicated that compared to the Control+AAV-NC group,the Stress+AAV-NC group had a significantly reduced mean fluorescence intensity of CB1R+ cells in the DG(P=0.008).After selective CB1R overexpression,the Stress+CB1R-OE group showed a significantly increased mean CB1R fluorescence intensity in the DG compared to the Stress+AAV-NC group(P＜0.001).Western blotting results showed that hippocampal CB1R protein expression was significantly lower in the Stress+AAV-NC group than in the Control+AAV-NC group(P=0.001).Compared to the Stress+AAV-NC group,the Stress+CB1R-OE group had a significantly increased hippocampal CB1R expression level(P＜0.001).Compared to the Control+AAV-NC group,the Stress+AAV-NC group had reduced densities of BrdU+ newborn cells(P=0.003)and BrdU+/NeuN+newly matured neurons(P=0.001)in the DG.After selective CB1R overexpression,the Stress+CB1R-OE group showed significantly increased densities of BrdU+ cells(P=0.035)and BrdU+/NeuN+ neurons(P=0.028)in the DG.No significant difference was observed in the mean NeuN fluorescence intensity in the DG among the three groups.Conclusion Selective overexpression of hippocampal CB1R can alleviate stress-mediated reduction in hippocampal neurogenesis and subsequently improve behavioral deficits in stress-induced rats.