| Objectives To explore the effects of propofol and low dose of ketamine on the spatial learning and memory function,the protein expression levels and function of N-methyl-D-aspartic acid receptor(NMDAR)and α-amino-3-hydroxy-5-methyl-4-isoxazole-propionic acid receptor(AMPAR),long-term potentiation(LTP)in the depressed rats undergoing electroconvulsive shock(ECS),with the aim to elucidate the role of NMDAR mediated metaplasticity in the protective effects of propofol and low dose of ketamine on the learning and memory function of depressed rats.Methods Part Ⅰ Male Sprague Dawley(SD)rats,aged 2~3 months,were used,and the chronic unpredictable mild stress(CUMS)was applied to establish the model rats of depression.Eighty depression model rats were assigned randomly to eight groups(n=10): group D,group DP,group DE,group DPE,group DK,group DKE,group DPKE,group DPME.Group D was treated with normal saline(8ml/kg,i.p.)and then sham ECS;group DP was treated with propofol(80mg/kg,i.p.)and then sham ECS;group DE was treated with normal saline(8ml/kg,i.p.)and then ECS;group DPE was treated with propofol(80mg/kg,i.p.)and then ECS;group DK was treated with ketamine(10mg/kg,i.p.);group DKE was treated with ketamine(10mg/kg,i.p.)and then ECS;group DPKE was treated with propofol(80mg/kg,i.p.)combined with ketamine(10mg/kg,i.p.)and then ECS;group DPME was treated with propofol(80mg/kg,i.p.),MK801(1mg/kg)and then ECS.All the treatments were performed once per day for 7 consecutive days.Group C was exposed to no treatment.The sucrose preference percentage(SPP)of sucrose preference test,the incidence of rearing and the amount of acrossing the grid of the open field test(OFT)were used to evaluate the depressive behavior;the escape latency(EL)and space exploration time(SPT)of Morris water maze were applied to evaluate the spatial learning and memory function;western-blot assay was used to determine the protein expression levels of NR1,NR2 A,NR2B,Glu R1 subunits.Part Ⅱ Male Sprague Dawley(SD)rats,aged 2~3 months,were used,and the chronic unpredictable mild stress(CUMS)was applied to establish the model rats of depression.Seventy-two depression model rats were assigned randomly to six groups(n=12): group D,group DE,group DK,group DPE,group DPKE,group DPME.The treatments for each group were perform according to the methods in the Part I.The NMDAR-mediated,AMPAR-mediated f EPSP in the Schaffer collaterals-CA1 pathway synapses of hippocampus were detected with extracellular recordings;the LTP in Schaffer collaterals-CA1 pathway synapses was induced with high frequency stimulus(HFS)of protocol 1 and protocol 2(the intensity of protocol 2 is higher than protocol 1);the f EPSP during the perfusion of a CSF containing propofol or ketamine was recorded.Results Part Ⅰ Experiment 1:(1)Before treatments,the SPPs of groups D,DE,DK were lower than that of group C(P<0.05),and no difference was found among groups D,DE,DK(P>0.05).After treatments,as compared with group D,the SPP,incidence of rearing,amount of acrossing the grid in group DE and group DK increased(P<0.01);the SPP and incidence of rearing of group DE were higher than that of DK(P<0.01).(2)Before treatments,the ELs of groups D,DE,DK were longer than that of group C while the SPTs were shorter in groups D,DE,DK than in group C,and no difference was found among groups D,DE,DK.After treatments,as compared with groups C,D,DK,the EL of group DE increased while the SPT decreased significantly(P<0.01),and no significant difference was found in the ELs or SPT between group D and group DK(P>0.05).(3)The expression levels of Glu R1 in groups D,DE,DK were lower than that in group C(P<0.01).As compared with group D,the expression levels of Glu R1 in group DE and DK increased significantly(P<0.01),and no significant difference was found between group DE and DK(P>0.05).The expression levels of NR1,NR2 A,and NR2 B in groups D,DE,DK were lower than that in group C(P<0.01).As compared with group D and DK,the expression levels of NR1,NR2 A,and NR2 B in group DE significantly decreased.The expression levels of NR1 and NR2 B were higher in group DK than in group D(P<0.01),and no significant difference was found in the NR2 A expression between these two groups(P>0.05).No significant difference was found in the ratio of expression levels of NR2B/NR2A(P>0.05).Experiment 2:(1)Before treatments,no difference in the SPP,incidence of rearing,amount of acrossing the grid was detected among groups D,DP,DE,DPE,DKE(P>0.05).After treatments,the SPPs,incidence of rearing,amount of acrossing grid of groups DE,DPE,DKE were higher than that of group D(P<0.01);as compared with group DE and DKE,the SPP in group DPE decreased,and no difference was found in incidence of rearing or amount of acrossing grid between group DE and group DPE(P>0.05);no significant difference was found in SPP between group DE and group DKE(P>0.05);the incidence of rearing and amount of acrossing grid of group DKE were higher than that of DE(P<0.01).(2)Before experimental treatments,no statistically significant difference in ELs or SPT among groups D,DP,DE,DPE,DKE was found.After treatments,as compared with group D,the ELs of group DE,DPE,DKE increased while the SPT decreased significantly(P<0.01),and the ELs in group DPE and DKE were shorter while the SPTs were longer than that in group DE(P<0.01);no significant difference was found in ELs or SPT between group D and group DP,nor between group DPE and DKE(P>0.05).(3)The expression levels of Glu R1 in groups DE,DPE,DKE were higher than that in group D(P<0.01).No significant difference was found between group D and group DP,nor among group DE,DPE and DKE(P>0.05).As compared with group D,the expression levels of NR1 and NR2 B in groups DE,DPE,DKE decreased(P<0.05),and the expression levels of NR1 and NR2 B were higher in the group DPE and group DKE than in group DE(P<0.05).As compared with group D,the expression levels of NR2 A decreased in group DE and DKE;the expression levels of NR2 A in group DPE was higher than that in group D and DKE.As compared with group D,the ratio of NR2B/NR2 A in group DKE increased,and that in group DPE decreased(P<0.05).No statistically significant difference was found among groups D,DP,DE(P>0.05).incidence of rearing,amount of acrossing the grid among groups D,DPE,DPKE,DPME(P>0.05)was found.After treatments,the SPPs,incidence of rearing,amount of acrossing the grid of groups DPE,DPKE,DPME were higher than that of group D(P<0.01);as compared with group DPE,the SPPs and incidence of rearing in group DPKE and group DPME increased(P<0.01);no significant difference was found in the SPP,incidence of rearing,amount of acrossing the grid between group DPKE and group DPME(P>0.05).Experiment 3:(1)Before treatments,no difference in the SPP,(2)Before treatment,no significant difference was found in EL or SPT among these four groups(P>0.05).After treatments,as compared with group DPE,the ELs of group DPKE and group DPME decreased(P<0.01),and the SPT increased significantly(P<0.01);no significant difference was found in EL or SPT among group D,DPKE,DPME(P>0.05).(3)The expression levels of Glu R1 in groups DPE,DPKE,and DPME were higher than that that in group D(P<0.01);furthermore,the expression level of Glu R1 in group DPKE was higher than that in group DPE(P<0.01);no significant difference was found between group DPE and group DPME(P>0.05).No difference was found in the NR1 expression among groups(P>0.05).As compared with group DPE,the expression levels of NR1,NR2 B,and ratio of NR2B/NR2 A in groups DPKE,DPME increased significantly(P<0.05);the expression levels of NR2 B in group DPKE and group DPME were higher than that in group D,and no significant difference was found in NR2 B expression between group DPKE and DPME(P>0.05);no difference was found in NR1 or NR2B/NR2 A among groups D,DPKE,DPME(P>0.05).Part Ⅱ Experiment 1:(1)As compared with group C,the NMDAR I/O in group D decreased(P<0.01);as compared with group D,the NMDAR I/O in Group DK increased but that in group DE decreased,with statistical significance(P<0.01).As compared with group C,the AMPAR mediated f EPSP in group D decreased(P<0.01);as compared with group D,the AMPAR mediated f EPSP in group DK and group DK increased,and the AMPAR mediated f EPSP was higher in group DE than that in group DK(P<0.01).(2)After stimulus with HFS protocol 1,as compared with group C,the LTP levels in group D,DE,DK decreased(P<0.01).The LTP level of group DE was lower than that in group D and group DK(P<0.01).No difference was found between group D and group DK(P>0.05).In group C and group DE,the protocol 2 induced higher levels of LTP than protocol 1,with statistical significance(P<0.05).In group D,LTP level after protocol 2 was also higher than that after protocol 1,but no statistical significance was determined(P>0.05).Experiment 2:(1)As compared with group DE,the NMDAR I/O in group DPE,DPKE,DPME increased(P<0.01);as compared with group DPE,the NMDAR I/O in group DPKE and group DPME increased;the NMDAR I/O in group DPME was lower than that in group DPKE(P<0.01).(2)After stimulus with HFS protocol 1,as compared with group DE,the LTP levels in group DPE,DPKE,DPME increased,with statistical significance(P<0.01);as compared with group DPE,the LTP levels of group DPKE and group DPME increased(P<0.01).No difference was found between group DPKE and group DPME(P>0.05).(3)Propofol of both 10μM and 20μM inhibited the f EPSP within the Schaffer collaterals-CA1 pathway significantly,and the inhibitory effect of 20μM was stronger than that of 10μM(P<0.001).Ketamine of 1μM showed no significant effect on the f EPSP within the Schaffer collaterals-CA1 pathway,and ketamine of 10μM increased the f EPSP slightly.But,no difference was found in the effects between 1μM and 10 μM on the f EPSP(P>0.05).Conclusions(1)The antidepressant efficacy of ECS maybe associated with up-regulating the expression of Glu R1 and function of AMPAR in hippocampus;the impairment of spatial learning and memory function maybe mediated by the down-regulation in the expression and function of NMDAR in Schaffer collaterals-CA1 pathway in hippocampus.(2)Propofol could partially reverse the ECS caused down-regulation in expression and function of NMDAR and alleviate the spatial learning and memory function;combined with propofol,the NMDAR antagonist(ketamine or MK801)could further reverse the ECS caused down-regulation in expression and function of NMDAR and alleviate the spatial learning and memory function.(4)The ECS down-regulates the expression and function of NMDAR and impairing the LTP and spatial learning and memory in depressed rats via activating the NMDAR mediated metaplasticity,and the propofol and ketamine increase the expression and function of NMDAR and improving the synaptic plasticity via inhibiting the NMDAR activity in ECS. |
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