To Explore From Glur2 Hypothesis The Effect Of Low-dose Ketamine Combined With Propofol On Learning And Memory Function In Depressive Rats Receiving Electroconvulsive Shock

Object To investigate the effect of low-dose ketamine combined with propofol on depressive-like behavior, learning and memory function and glutamate receptor 2 in depressive rats undergoing electroconvulsive shock, and further explore the underlying molecular mechanisim that low-dose ketamine combined with propofol to alleviate learning and memory impairement in depressive rats undergoing electroconvulsive shock.MethodsPartⅠFifty healthy adult male Sprague–Dawley rats, 2~3 months, weighing 200~250g, were randomly assigned into 5 groups(n=10 in each group): control group(group C), depressive-like behavior group(group D), ECS group(group DE), propofol group(group DP), ECS combined with propofol group(group DEP). Group C was the control group without any treatments, Group D, DE, DP and DEP were received chronic unpredictable mild stress to establish depression model. After the CUMS procedure was completed, rats in group D were injected normal saline(8mL/kg, i.p.) and then subjected to sham ECS; rats in group DE were injected normal saline(8mL/kg, i.p.) and then received to ECS treatment; rats in group DP were injected propofol(80mg/kg, i.p.) and then subjected to sham ECS; rats in group DEP were injected propofol(80mg/kg, i.p.) and then subjected to ECS treatment. The sham ECS was handlded identically as ECS without current. The aforementioned treatments were given once a day for 7 days. Sucrose preference test and open-field test were used to evaluate the depressive-like behavior before and after CUMS, after ECS treatment; Morris water maze was used to evaluate the learning/memory function after ECS. The expression level of GluR2, p-GluR2, ADAR2, PKC were measured by Western-blot; the expression level of GluR2, ADAR2 mRNA were measured by RT-PCR; the numbers of neurons in CA1 area of hippocampus were measured by Nissal staining.PartⅡForty healthy adult male Sprague–Dawley rats, 2~3 months, weighing 200~250g, were randomly assigned to 4 groups(n=10 in each group): depression group(group D), ketamine group(group DK), ECS combined with propofol group(group DEP), ECS+propofol+ketamine group(group DEPK). All rats were treated with chronic unpredictable mild stress(CUMS) to establish depression model. After the CUMS procedure was completed, rats in group D were injected normal saline(8mL/kg, i.p.) and then subjected to sham ECS; rats in group DK were injected ketamine(10mg/kg, i.p.) and then received to ECS treatment; rats in group DEP were injected propofol(80mg/kg, i.p.) and then subjected to ECS; rats in group DEPK were injected propofol(80mg/kg, i.p.) combined with ketamine(10mg/kg, i.p.) and then subjected to ECS treatment. The sham ECS was handlded identically as ECS without current. The aforementioned treatments were given once a day for 7 days. The behavioral test and biochemical assays were identical to the first part of the experiment.ResultsPartⅠ(1) Sucrose preference test and open-field test: Before CUMS, rats in each groups showed similar sucrose preference percentage(SPP) and the numbers of crossed squares and rearing. After CUMS, rats in CUMS-treated groups exhibited significantly decreased SPP and the numbers of crossed squares and rearing compared with group C, while those valus among the four CUMS-treated groups were not significantly different. After ECS treatment, the SPP and numbers of crossed squares and rearing exhibited significantly increased in group DE and DEP compared with group D. However, the numbers of crossed square and rearing showed decreased in group DEP in compareson of group DE.(2) Morris water maze: The swimming speed of rats in different times were similar. Compared with group C, CUMS-treated rats exhibited increased eacape latencies and decreasd space exploration time. Compared with group D, rats in group DE and DEP exhibited increased eacape latencies and decreasd space exploration time, while rats in group DEP showed decreased eacape latencies and increased space exploration time compared with group DE.(3) Biochemical assays: Compared with group C, CUMS-treated rats exhibited decreased numbers of neurons in CA1 area of hippocampus, while there were no significant defferences among CUMS-treated groups. Compared with group D, the expression level of GluR2 mRNA down-regulated in group DE, while the expression level of GluR2 mRNA up-regulated in group DEP in compareson with group DE. There were no significant defferences among five groups of ADAR2 mRNA. Compared with group D, the expression level of GluR2 protein down-regulated, p-GluR2 protein and PKC protein up-regulated in group DE, while the expression level of GluR2 protein up-regulated, p-GluR2 protein and PKC protein down-regulated in group DEP in compareson with group DE. There were no significant defferences among five groups of ADAR2 protein.PartⅡ(1) Sucrose preference test: Before and after CUMS, rats in each groups showed similar sucrose preference percentage(SPP). After ECS treatment, the SPP exhibited significantly increased in group DK, DEP and DEPK compared with group D. Rats in group DEPK showed the most SPP than group DEP and DK.(2) Morris water maze: The swimming speed of rats in different times were similar. After ECS, compared with group D, rats in group DEP exhibited increased eacape latencies and decreasd space exploration time, and rats in group DEPK exhibited decreased eacape latencies and increasd space exploration time. There were no significant differences between group D and group DK in eacape latencies and space exploration time.(3) Biochemical assays: There were no significant differences among four groups in the numbers of neurons in CA1 area of hippocampus. Compared with group D, the expression level of GluR2 mRNA down-regulated in group DEP, while the expression level of GluR2 mRNA up-regulated in group DEPK in compareson with group DEP. There were no significant defferences among four groups of ADAR2 mRNA. Compared with group D, the expression level of GluR2 protein down-regulated, p-GluR2 protein and PKC protein up-regulated in group DEP, while the expression level of GluR2 protein up-regulated, p-GluR2 protein and PKC protein down-regulated in group DEPK in compareson with group DEP. There were no significant defferences among four groups of ADAR2 protein.Conclusins(1) ECS has a good antidepression effect, but could induce learning and memory function impairment. The underlying molecular mechanism of learning and memory impairment induced by ECS was associated with low expression level of GluR2.(2) Propofol could effectively alleviate learning/memory impairment induced by ECS. This cognitive protective effect of propofol was mainly attributed to reduce the expression level of PKC, so as to increase the expression level of GluR2. However, propofol could moderately weakened the antidepressant effect of ECS.(3) Low-dose ketamine could strengthen the antidepressant effect of ECS under propofol anesthesia, and further alleviate learning/memory impairment induced by ECS, the underlying mechanisim was attributed to alleviate further PKC-GluR2 pathway impairment induced by ECS.