神经病理性疼痛老年大鼠海马CA1区突触长时程增强的变化

Changes of long-term potentiation in hippocampal CA1 area in old rats with neuropathic pain

目的观察神经病理性疼痛老年大鼠海马CA1区突触长时程增强(LTP)的变化。方法老年雄性Wistar大鼠15只,随机均分为三组。模型组,结扎左侧L4/L5脊神经;D-2-氨基-5-磷酸戊酸(AP5)组,侧脑室输注AP5,余同模型组;假手术组,操作同模型组,但不结扎。观察大鼠行为变化,连续3周测定大鼠电痛阈值,1次/周;记录海马CA1区树突层兴奋性突触后膜电位(EPSP)、输入/输出曲线及LTP的变化。结果模型组与AP5组大鼠术后行为异常,术后各时点电痛阈值低于术前值及假手术组相应时点值(P<0.05);三组基础EPSP幅值稳定,最大基础EPSP幅值的50%组间比较差异无统计学意义;模型组LTP高于其他两组(P<0.05)。结论结扎老年大鼠L4/L5脊神经所致的神经病理性疼痛,不干扰海马CA1区突触及锥体细胞兴奋性,但可易化该区突触LTP。

Objective To observe the. changes of long-term potentiation （LTP） in the hippocampal CA1 area in old rats with neuropathic pain by L4/L5 spinal nerve ligation. Methods Fifteen old male Wistar rats were randomly divided into 3 groups with 5 rats each. Model group received ligation of left L4/L5 spinal nerves, AP5 group received the same as model group except infusing APS（i. c. v）,and the left L4/L5 spinal nerve were exposed but not ligated in sham operating group. The changes of rat behaviour were observed. The pain threshold by electric stimuli was measured once a week for 3 weeks. The changes of excitatory post-synaptic potential （EPSP） and input/output curve and LTP of the CA1 stratum radiatum of the rat hippocampus were respectively observed by stereotaxic technology and extracellular recording. Results In model and AP5 groups, the rats＇ behaviour was significantly abnormal after operation, and the pain threshold was significantly decreased as compared to those before operation and lower than those in sham operating group （P〈0.05）. The baseline EPSP amplitude of all groups was stable. A half of maximal baseline EPSP amplitude of three groups was not significantly different. The LTP amplitude of model group was higher than that of the other groups （P〈 0. 05）. Conclusion The results suggest that the neuropathic pain by L4/L5 old rat spinal nerve ligation might not disturb the excitability of synapse and pyramidal neuron in the CA1 area of the hippocampus, but facilitate LTP induction.