| Objective:To investigate the ameliorative effects of dexmedetomidine on synaptic plasticity and cognitive dysfunction in sleep-deprived rats based on the Wnt/β-catenin signaling pathway.Methods:Forty male Sprague-Dawley rats,weighing 300-350 g,were selected at 3 to 4 months of age.The rats were divided into 4 groups(n=10)using the random number table method: a natural sleep group used as the control(N group),an experimental group subjected to sleep deprivation(SD group),a sleep deprivation and dexmedetomidine group(SDD group),and a sleep deprivation,dexmedetomidine and Wnt pathway inhibitor group(SDX group).In the control(N)group,rats maintained natural sleep patterns.The rats in the experimental groups were subjected to sleep deprivation lasting 20 hours daily(12:00-8:00 the next day)for 21 consecutive days using a modified multi-platform water environment method.After sleep deprivation,rats in the SDD group received dexmedetomidine(20μg/kg)injected intraperitoneally for three consecutive days,while rats in the SDX group received dexmedetomidine(20 μg/kg)and the Wnt pathway inhibitor XAV-939(100 μL,2 mg/m L).Equal amounts of saline were injected intraperitoneally into rats in the N and SD groups.On day 25,the Morris water maze was used to assess the spatial learning and memory ability of each group of rats.The rats were then anesthetized intraperitoneally with tribromoethanol prior to brain removal.Three rats from each group were selected for hippocampal tissue sampling and sectioning.Golgi staining was used to assess the density of neuronal dendritic spines in the CA1 region of the hippocampi of rats from each group.To further explore the underlying molecular mechanism,mRNA expression levels of Wnt7 a,GSK-3β and β-catenin were measured using RT-qPCR,while protein expression levels of Wnt7 a,GSK-3β and β-catenin were assessed by Western blotting.Results:1.The results of the water maze showed that there was no statistically significant difference in the swimming speed of rats among the groups(P > 0.05),neither was there any significant difference in the escape latency among the groups(P > 0.05)on the first day of the positioning navigation experiment.From the second day onwards,escape latency gradually decreased with increasing training time in all groups.Compared to the N group,rats in the SD group had a significantly longer escape latency,while exhibiting a lower number of platform crossings and less percentage of time spent in the target quadrant,and the differences were statistically significant(P<0.05).SDD group rats in turn exhibited significantly shorter escape latency and an increased number of platform crossings and more percentage of time spent in the target quadrant relative to rats in the SD group(P < 0.05).Rats in the SDX group had a longer escape latency and a lower number of platform crossings and less percentage of time spent in the target quadrant relative to the SDD group,and the differences were statistically significant(P < 0.05).2.Golgi staining revealed that the density of neuronal synaptic spines in the hippocampal CA1 region was lower in the SD group than in the N and SDD groups(P < 0.05),and the density of dendritic spines in the SDD group was higher than in the SD group,and the difference was statistically significant(P < 0.05).The density of dendritic spines in the SDX group was significantly lower than in the SDD group(P < 0.05),and the difference was not statistically significant(P > 0.05)with the SD group.3.RT-qPCR revealed that the hippocampi of rats in the SD group exhibited higher mRNA expressions of Wnt7 a and β-catenin,and lower mRNA expression of GSK-3β relative to rats of the N group,and the differences were statistically significant(P < 0.05).The hippocampi of rats in the SDD group had significantly(P < 0.05)higher mRNA expressions of Wnt7 a and β-catenin,and lower mRNA expression of GSK-3β when compared to rats in the SD group,and the differences were statistically significant(P < 0.05).Hippocampi of rats in the SDX group exhibited significantly(P < 0.05)higher mRNA expressions of Wnt7 a andβ-catenin and lower mRNA expression of GSK-3β when compared to SDD group rats,and the differences were statistically significant(P < 0.05).4.Western blotting demonstrated that GSK-3β protein expression was higher and Wnt7 a and β-catenin protein expressions were lower in the SD group relative to the N group(P <0.05).In the SDD group,GSK-3β protein expression was lower while Wnt7 a and β-catenin protein expressions were higher compared to rats of the SD group after three consecutive days of intraperitoneal injection of dexmedetomidine,and the differences were statistically significant(P < 0.05).Meanwhile,rats in the SDX group exhibited increased GSK-3β protein expression and decreased Wnt7 a and β-catenin protein expressions relative to the SDD group,and the differences were statistically significant(P < 0.05).Conclusion:Dexmedetomidine can improve cognitive function in sleep deprived rats,via a mechanism which may be related to activation of the Wnt/β-catenin pathway and improvement of hippocampal synaptic structural plasticity. |
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