Effects Of Neuropathic Pain On Learning And Memory And Synaptic Plasticity Of Hippocampus In Aged Rats

Objective:To investigate the effects of neuropathic pain on the ability of learning and memory, and the level of protein S100B in cerebrospinal fluid(CSF),the change of synaptic structure of CA1 area in the hippocampus.Methods:Total 60 male 18-month-old Wistar rats, randomly divided into 3 groups:normal group (N),sham group(S),CCI group(C),the CCI(chronic constriction nerve injury) model with chronic sciatic nerve ligation, then each group randomly divided into 4 groups at 1st,7th,14th,21th day. PWTL was tested, and the ability of learning and memory were assessed with the Morris water maze (MWM), the concentration of protein S100B in CSF was detected by ELISA after anesthesia respectively. The changes of Gray I synaptic structure of hippocampus was observed with transmission electron microscope.Results:1) In group C, the PWTL was significantly decreased significantly after operation, there was no significant difference between group N and group S.2) Compared with group N and group S, the escape latency in group C was observed significantly longer than before (P<0.01), and the time consumption across the original platform in the spatial probe test in group C was less than that in group N and S (P<0.01).3) Compared with group N and group S, the concentration of protein S100B of group C was significantly increased (p<0.01).4) The width of synaptic cleft increased, and the postsynaptic densities decreased, synaptic vesicles density decreased with transmission electron microscope significantly.Conclusion:Neuropathic pain impairs the ability of spatial learning and memory in aged rats, up-regulation of protein S100B expression in the CSF, and synaptic plasticity of hippocampus may be involved in the mechanism.