Effects of activated microglia in the prefrontal cortex on long-term spatial memory function in mice with post-stroke depression / 中华行为医学与脑科学杂志

ABSTRACT

Objective:To investigate the effect of activation of microglia in prefrontal cortex on long-term spatial memory in post-stroke depression mice.Methods:Forty-eight male C57BL/6 mice were divided into sham operation group, stroke group, post-stroke depression group and depression group according to the random number table method with 12 in each group, and 36 mice were divided into solvent group, enrofloxacin group and minocycline group according to the random number table method with 12 in each group.Middle cerebral artery occlusion (MCAO) was use to establish the stroke model, and forced swimming was used to establish the depression model.The post-stroke depression model mice were received MCAO first and then received forced swimming on the 4th day after stroke to establish the model.Mice in enrofloxacin group and minocycline group were treated with enrofloxacin and minocycline injection once a clay for 14 days from the 5th day after stroke, respectively.Forced swimming test and sugar water preference test were used to evaluate the depression of mice in each group, Morris water maze test was used to detect the spatial memory function of mice in each group, and Nissl staining and immunofluorescence staining were used to detect the neuronal function and the number and type of microglia activation.The expression of inflammatory cytokines IL-6 and IL-1β were detected by Western blot.GraphPad Prism 8.0.1 statistical software was used for statistical analysis.The single factor variance analysis was used to compare the difference among multiple groups, and pairwise comparison was performed with SNK- q test. Results:(1) There were statistically significant differences in depression, learning and memory, neuron damage, activation of microglia, inflammatory factors and other indicators in sham operation group, stroke group, post-stroke depression group and depression group ( F=43.58-255.70, all P<0.05). Compared with stroke group, post-stroke depression group had longer floating immobility time ((222.70±29.12) s, (79.25±46.78) s, P<0.05), the preference rate of sugar water was significantly lower ( (49.44±6.19) %, (84.49±4.73) %, P<0.05), and the average value of platform approach after correction was higher((125.00±9.95) mm, (96.79±12.57) mm, P<0.05), Nissl bodies expression was lower ((53.50±15.78) cells /mm 2, (85.67±17.52) cells /mm 2, P<0.05), NeuN positive expression rate was lower ((29.78±3.70) %, (45.73±4.51) %, P<0.05), the percent of M1 microglia expression was significantly higher ((75.55±8.84) %, (58.19±5.69) %, P<0.05), the percent of M2 microglia expression was lower ((43.46±5.11)%, (57.14±5.40)%, P<0.05), and the expression levels of IL-6 ((1.14±0.03), (0.94±0.05), P<0.05) and IL-1β((1.17±0.03), (0.56±0.04), P<0.05) were significantly higher.(2) Depression, learning and memory, neuron injury, activation of microglia, inflammatory factors and other indicators of mice in solvent group, enrofloxacin group and minocycline group were significantly different ( F=7.13-94.35, all P<0.05). Compared with enrofloxacin group, mice in minocycline group had shorter floating immobility time ((169.30±13.04) s, (224.30±22.60) s, P<0.05) and higher sugar water preference rate ((62.81±7.75) %, (47.71±8.11) %, P<0.05), the mean value of platform approach estimation after water maze correction was lower ((97.66±14.56) mm, (120.20±12.08) mm, P<0.05), and the expression level of Nissl bodies was higher ((80.17±10.55) cells /mm 2, (52.00±8.94) cells /mm 2, P<0.05), NeuN expression rate was high ((45.04±3.62) %, (28.88±4.50) %, P<0.05), Iba-1 expression was lower ((97.33±10.67) cells/mm 2, (112.50±6.54)cells/mm 2, P<0.05), the percent of M1 microglia expression was lower ((54.43±5.22) %, (73.82±6.88) %, P<0.05), and the percent of M2 microglia expression was significantly higher ((51.86±6.22) %, (36.30±5.72) %, P<0.05). The expression levels of IL-6 ((0.75±0.06), (1.21±0.07), P<0.05) and IL-1β ((0.61±0.06) (1.09±0.09), P<0.05) were lower. Conclusion:The long-term spatial memory impairment of post-stroke depression mice is aggravated, which is related to the neuron damage caused by increased activation of M1 microglia in PFC area.Inhibition of M1 microglia by minocycline can effectively improve the spatial memory ability of mice.