The Expression Of Hippocampal NMDA Receptors In The Neuropathic Pain Related Anxiety-like Behaviors In Rats

Objective:The aim of this study is to explore the expression and possible role of hippocampal NMDA receptors in the neuropathic pain related anxiety-like behaviors in rats.Methods:Adult male SD rats were used in this study. The model of neuropathic pain was established by partial sciatic nerve ligation, control group was performed by only exposing sciatic nerve without nerve ligation. The von Frey test was employed to assess the mechanical withdraw threshold. Open field test and Elevated plus-maze test were used to assess the anxiety-like behaviors; Sucrose preference test and Forced swimming test were used to assess the depression-like behaviors after28days injury. The expression of NMDA receptors and other synapse-associated proteins were investigated by Western Blot and Immunohistochemistry.Results:The mechanical withdraw threshold was significantly lower in partial sciatic nerve ligation rats compared to control rats (p<0.001), and it last till28days. In Open field test, the partial sciatic nerve ligation rats spent significantly less time in the central zone than control rats (p<0.05), there were no difference of locomotor activities between the two groups; in the Elevated plus-maze test, the partial sciatic nerve ligation rats spent significantly less time in the open arms than control rats (p<0.05), no differences were found in the locomotor activities. In the Sucrose preference test and the Forced swimming test, no differences were found in the ratio of sucrose preference and immobility time. Western Blot and Immunohistochemistry showed that the expression of NR1and NR2.B in hippocampus were significantly decreased (p<0.001) in partial sciatic nerve ligation rats while no alterations were found in the expressions of VGAT, GAD67, NR2A, GluRl, GluR2compared with control rats. Moreover, the expression of p-ERK1/2(p<0.01) and p-CREB (p<0.05) were also significantly decreasd in partial sciatic nerve ligation rats compared with control rats.Conclusion:The rats after partial sciatic nerve ligation showed significantly anxiety-like behaviors without depression-like behaviors28days after injury, the hippocampal NMDA receptos and ERK-CREB signaling pathway maybe involved in the behavior.