Effect of PSD-95 on long-term learning and memory impairment in neonatal rats induced by sevoflurane anesthesia / 中华行为医学与脑科学杂志

ABSTRACT

Objective:To investigate the effect of postsynaptic density-95(PSD-95)on long-term learning and memory impairment in neonatal rats induced by sevoflurane anesthesia.Methods:A total of 54 SD rats aged 7 days of SPF grade were randomly divided into 3 groups control group (exposed to air), model group (exposed to 2.1% sevoflurane, 4 h/d, consecutive 3 days) and PSD-95 inhibitor group (inhaled sevoflurane+ intraperitoneal injection NA-1, consecutive 5 days), with 18 rats in each group.Morris water maze test and new object recognition test were used to detect the ability of visuospatial learning and memory and recognition memory of rats in each group.RT-qPCR was used to detect the mRNA levels of kalirin, Rac1 and PSD-95 in rat hippocampus.The expressions of kalirin, Rac1, PSD-95 and apoptosis related proteins Caspase-3, Bcl-2 and Bax in rat hippocampus were detected by Western blot.The expression levels of kalirin and Rac1 in hippocampus were detected by immunohistochemistry.SPSS 23.0 software was used for statistical analysis.Repeated measurement ANOVA and one-way ANOVA was used for comparing among groups.Results:Repeated measurement ANOVA showed that in the water maze test, the interaction between time and group of platform seeking latency and swimming distance of the three groups were significant ( Ftime×group=36.539, 41.548, both P<0.01). Simple effect analysis showed that the platform latency and swimming distance in the model group from day 2 to 6 were longer than those in the control group (platform latency from day 2 to 6 t=14.039, 17.147, 13.155, 13.831, 27.247, all P<0.01; swimming distance from day 2 to 6 t=10.122, 20.987, 7.267, 10.011, 8.121, all P<0.01). Compared with the model group, from day 2 to 6, the platform latencies of PSD-95 inhibitor group were prolonged( t=7.948, 14.768, 11.582, 12.832, 24.346, all P<0.01) and the swimming distances were increased( t=8.235, 24.325, 11.234, 12.031, 7.036, all P<0.01). The new object recognition test found that the new object exploration time in the model group was significantly longer than that in the control group ((21.30±2.27)s, (19.21±1.42)s, t=1.843, P<0.01), and the new object exploration time in the PSD-95 inhibitor group was significantly longer than that in the model group ((26.83±2.13)s, t=4.844, P<0.01). The difference index of novel objects in the model group was significantly lower than that in the control group ((0.41±0.12), (0.59±0.10), t=3.416, P<0.01), and the difference index of novel objects in the PSD-95 inhibitor group was significantly lower than that in the model group ((0.37±0.08), t=0.696, P<0.05). The qRT-PCR results showed that the expressions of Rac1, kalirin and PSD-95 mRNA in the model group were significantly lower than those in the control group ( t=9.969, 3.954, 6.561, P<0.05), and the expressions of Rac1, kalirin and PSD-95 mRNA in the PSD-95 inhibitor group were significantly lower than those of the model group ( t=2.132, 2.251, 3.502, all P<0.05). Immunohistochemistry results showed that the kalirin in the hippocampus CA1 area of the model group was significantly lower than that in the control group((8.18±1.94) vs (15.47±3.35), t=11.47, P<0.01), and kalirin in the PSD-95 inhibitor group was significantly lower than that in the model group((4.98±1.53), t=10.28, P<0.01); Rac1 in the model group was significantly lower than that in the control group ((3.72±1.53), (8.17±2.91), t=6.76, P<0.01), and the Rac1 in the PSD-95 inhibitor group(2.73±0.37) was significantly lower than the model group ( t=4.72, P<0.05). Western blot results showed that Caspase-3((1.37±0.16) vs (0.54±0.01), t=5.71, P<0.01) and Bax((1.87±0.31) vs (1.23±0.25), t=12.01, P<0.01) protein levels in the model group were significantly higher than those in the control group.Caspase-3 and Bax protein levels in the PSD-95 inhibitor group were significantly higher than those in model group (Caspase-3 (1.79±0.17), t=9.87, P<0.01; Bax (2.19±0.21), t=16.19, P<0.01). The Bcl-2 protein level in the model group was significantly lower than that of the control group ((1.22±0.21) vs (1.96±0.38), t=11.92, P<0.01). And the Bcl-2 protein level in the PSD-95 inhibitor group (1.01±0.19) was significantly lower than that in the model group ( t=10.73, P<0.01). Conclusion:Sevoflurane anesthesia can damage the long-term learning and memory function and reduce the expression of PSD95 protein in neonatal rats.Inhibiting the expression of PSD95 can aggravate this damage, which may be related to the synaptic plasticity and apoptosis of neurons involved in PSD95.