摘要
目的:探讨吗啡对神经损伤性大鼠脊髓背角投射神经元诱发放电的影响及其作用机制。方法:采用Chung模型建立慢性神经性疼痛大鼠模型,行为学方法测试机械刺激缩足阈值判断模型是否成功。单个神经元记录法记录脊髓背角投射神经元放电活动。实验分正常大鼠组(N组),假手术组(S)和神经损伤性大鼠组(I组)。3组在脊髓表面予以吗啡、荷包牡丹碱(BIC)和番木鳖碱(STN)前后,以不同级别机械刺激足部感受野,分别记录脊髓背角投射神经元诱发放电活动。结果:脊髓表面用10μmol/L吗啡能显著抑制3组大鼠脊髓背角投射神经元的诱发性放电活动。与基础值相比,N组和S组压力刺激抑制了72%±6%(P<0.05),钳夹刺激抑制了76%±5%(P<0.05),但I组抑制作用显著低于N组和S组,压力与钳夹刺激与基础值比分别抑制32%±4%和26%±3%(P<0.05);而予以BIC阻断GABAA受体后,N组和S组吗啡的抑制作用明显减弱(P<0.05),I组吗啡的抑制作用无明显改变(P>0.05);STN阻断甘氨酸受体后,3组吗啡的抑制作用无明显区别;GABAA受体和甘氨酸受体同时阻断后,吗啡无明显抑制作用。结论:吗啡对慢性神经损伤性大鼠脊髓背角投射神经元诱发性放电活动的抑制作用明显减弱,主要与慢性神经损伤性大鼠脊髓GABA减少有关。
Objective To explore the inhibitory effect of spinal topical morphine on the dorsal horn projection neurons in nerve-injured rats and its mechanism. Methods Single-unit activity of dorsal horn projection neurons was recorded in anesthetized L5/L6 nerve-ligated rats. Allodynia was determined by a behavior test in nerve-injured rats. The evoked neuronal responses to mechanical stimuli applied to the receptive field were determined before and after the spinal topical application of morphine, bicuculline plus morphine, strychnine plus morphine, and both bicuculline and strychnine plus morphine in normal, sham operation, and nerve-injured rats. Results Spinal topical application of 10μmol/L morphine significantly inhibited the evoked responses of dorsal horn projection neurons in normal, sham, operation and nerve-injured rats. However, the inhibitory effect of morphine was significantly reduced in nerve-injured rats compared with that in normal and sham operation rats. Furthermore, the topical application of 20μmol/L bicuculline had little effect on the inhibitory effect of morphine in nerve-injured rats but it almost abolished the effect of morphine in normal and sham operation rats. The glycine receptor antagonist strychnine at 4μmol/L significantly decreased the effect of morphine in nerve-injured, normal, and sham operation rats. Conclusion The loss of tonic GABAergic inhibition contributes to the reduced inhibitory effect of morphine on dorsal horn projection neurons in nerve-injured rats.
出处
《中南大学学报（医学版）》
CAS
CSCD
北大核心
2006年第4期534-537,共4页
Journal of Central South University ：Medical Science
基金
湖南省卫生厅项目(B2005046)
