Effects Of Chronic Stress On Spatial Learning And Memory In Rats And Preliminary Study Of Its Mechanism

Objective:To observe the changes of extracellular level of amino acids in the hippocampal dentate gyrus(DG)in a rat model of chronic stress during Morris water maze(MWM)test,and primarily investigate the neurochemical mechanism responsible for effect of chronic stress on spatial learning and memory.Metnods:The rat model of chronic stress(CS)was prepared by random application of varied stressors,and then the extracellular concentrations of glutamine(Gln),taurine(Tau),asparate(Asp),glutamate(Glu)and glycine(Gly)in the DG were determined by in vivo microdialysis and HPLC.Next,the spatial learning and memory abilities of rats were assessed by Morris water maze(MWM),and the extracellular concentrations of the amino acids in the DG were simultaneously observed.Result:(1)Compared with the control group,the extracellular concentrations of Glu,Gln and Tau in hippocampal DG were significantly increased in CS group(P<0.05,respectively),despite the levels of Asp and Gly did not changed(P>0.05,respectively).(2)In the place navigation trial of MWM test,the escape latency decreased in both control and CS groups over the course of the training days,however,on the 4th day,escape latency was significantly shorter in CS group compared with control group(P<0.05).(3)In the spatial prove trial of MWM test,the number of platform crossings was markedly increased in CS group compared with control group(P<0.05).(4)In control group,the extracellular concentration of Glu in the DG was significantly increased during MWM test,and the increases were enhanced in CS group(P<0.05).(5)During MWM test,Tau level in the DG was significantly increased in CS group(P<0.05),while it was not changed in control group(P>0.05).(6)In CS group,both Asp and Gly levels in the DG were significantly decreased on the 5th and 1st day respectively,while Gln level did not appear a significant change;there were no significant differences between the two groupsConclusion:Chronic stress facilitates the spatial learning and memory in rats,which may be related to the increase of Glu,Gln and Tau in hippocampal DG region.