| Objective:Neurogranin(Ng),a neurosystem-specific postsynaptic proteins,has been found as a new diagnostic marker for cognitive impairment in recent years of research.In this study,Loxp-Cre gene editing technology was used to specifically knock out Ng genes in the nervous system,so as to explore whether swimming regulates Ng to improve the spatial memory function of mouse model with chronic hypoperfusion cerebral ischemia,and to explore the mechanism of Ng regulation of hippocampal synaptic plasticity in improving spatial memory in swimming.Methods:The mouse model of chronic hypoperfusion cerebral ischemia was established by the bilateral common carotid artery stenosis(BCAS).42 of C57/B6 mice were randomly divided into the operation group(n=30)and the Sham operation group(n=12).The mice in the operation group underwent bilateral common carotid artery stenosis,while the sham operation group only separated the bilateral common carotid arteries without narrow.Laser speckle imaging technology was used to measure the cerebral blood flow,and T-maze was used to detect whether the spatial memory was damaged.Based on the results above,24 mice of the operation group were modled successfully and were randomly divided into the BCAS group and the Swimming group,12 mice in each group.32 of Ng knockout mice underwent the bilateral common carotid artery stenosis,and were tested with the Laser speckle imaging technology and T-maze test.24 mice of the Ng knockout mice were modled successfully and were randomly divided into the BCAS + Ng KO group and the Swimming + Ng KO group,12 mice in each group.The Swimming group and the Swimming + Ng KO group underwent swimming intervention on one week after surgery.The Swimming training was performed for 1 week of adaptation period and 4 weeks of training period,60 min each day,5 days each week in the Swimming group and the Swimming + Ng KO group.After intervention,T-maze and Morris water maze were used to detect the changes of spatial memory behaviors.Patch clamp electrophysiological technique was used to detect the change of long-term potentiation(LTP)of hippocampal CA3-CA1.The expression levels of Ng,CaM and CaMKII in hippocampal tissues were detected by western blot.Results:(1)Effects of swimming on spatial memory ability in mice with chronic hypoperfusion cerebral ischemia.Before the intervention,the results of T-maze test showed that,compared with the Sham operation group,the spontaneous alternations rate of the BCAS group,the Swimming group,the BCAS + Ng KO group and the Swimming + Ng KO group all decreased(P=0.025,P=0.012,P=0.001,P=0.001).After the intervention,compared with the Sham operation group,the spontaneous alternation rate of the BCAS group was decreased(P<0.001),and the spontaneous alternation rate of the Swimming group is higher than the BCAS group(P<0.001),and BCAS + Ng KO spontaneous alternation rate is lower than that of the BCAS group(P=0.032),and the spontaneous alternation rate of the Swimming + Ng KO group is lower than the Swimming group(P<0.001).The results of the Morris water maze showed that after intervention,the escape latency of the BCAS group was longer than the Sham operation group on day 2 and day 4 of directional navigation learning(P<0.001).On day 2,day 3,and day 4 of directional navigation learning,the escape latency of the Swimming group was shorter than that of the BCAS group(P<0.001,P=0.037,P<0.001),while the escape latency of the Swimming group was shorter than that of the Swimming + Ng KO group(P<0.001,P=0.014,P<0.001).In space exploration test of the water maze,the times of crossing the platform of the BCAS group was less than the Sham operation group(P<0.001),and the times of crossing the platform in the Swimming group was more than the BCAS group(P=0.040),and the times of crossing the platform in the BCAS + Ng KO group was less than the BCAS group(P=0.033),and the times of crossing the platform in the Swimming + Ng KO group was less than the Swimming group(P=0.022).(2)Effects of swimming on hippocampal LTP in mice with chronic hypoperfusion cerebral ischemia.Compared with the Sham operation group,the excitatory postsynaptic potential(field excitatory postsynaptic potential,fEPSP)slope of the BCAS group was decreased after 100 Hz single pulse stimulating hippocampal CA1-CA3(P<0.001).Compared with the BCAS group,the fEPSP slope of hippocampus CA3-CA1 in the Swimming group was increased(P=0.037).Compared with the BCAS group,the fEPSP slope of hippocampus CA3-CA1 in the BCAS + Ng KO group was decreased(P=0.029).Compared with the Swimming + Ng KO group,the fEPSP slope of hippocampus CA3-CA1 of the Swimming group was increased(P=0.011).(3)Effects of swimming on the expressions of the proteins associated with hippocampal synapses in mice with chronic hypoperfusion cerebral ischemia.The protein expression of Ng in the BCAS group was lower than the Sham operation group(P=0.003),and the protein expression of Ng in the Swimming group was higher than the BCAS group(P=0.029),and the protein expression of Ng in the BCAS + Ng KO group was lower than the BCAS group(P=0.020),and the protein expression of Ng in the Swimming + Ng KO group was lower than the Swimming group(P<0.001),the BCAS + Ng KO group compared with the Swimming + Ng KO groups had no difference(P=0.950).The protein expression of CaM in the BCAS group was lower than the Sham operation group(P=0.006),and the protein expression of CaM in the Swimming group was higher than the BCAS group(P=0.026),and the protein expression of CaM in the BCAS + Ng KO group was lower than the BCAS group(P=0.047),and the protein expression of CaM in the Swimming + Ng KO group was lower than the Swimming group(P=0.003),and the BCAS + Ng KO group compared with the Swimming + Ng KO groups had no difference(P = 0.367).The protein expression of CaMKII in the BCAS group was lower than the Sham operation group(P=0.003),and the protein expression of CaM in the Swimming group was higher than the BCAS group(P=0.044),and the protein expression of CaM in the BCAS + Ng KO group was lower than the BCAS group(P=0.026),and the protein expression of CaM in the Swimming + Ng KO group was lower than the Swimming group(P=0.002),and there was no difference between the BCAS + Ng KO group and the Swimming + Ng KO group(P=0.490).Conclusion:This study demonstrated that swimming could improve the spatial memory ability of vascular cognitive impairment induced by chronic hypoperfusion cerebral ischemia,and the regulation of Ng to regulate the long-term potentiation of hippocampus and activate the calcium signal transduction of synaptic plasticity is one of its mechanisms. |
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