GABA_A受体对神经病理性痛大鼠海马长时程增强维持的影响

Effect of GABA_A receptor on maintenance of synaptic long-term potentiation in hippocampus in rats with neuropathic pain

目的:探讨GABAA受体对神经病理性痛大鼠海马CA1区突触长时程增强(long-term potentiation,LTP)维持的影响。方法:成年雄性Wistar大鼠18只,随机均分为三组:神经病理性痛模型组(NP组)、荷包牡丹碱1组(B1组)、荷包牡丹碱2组(B2组)。采用结扎L_(4,5)左侧脊神经的方法制备大鼠模型。于模型制备后1、2和3周观察大鼠痛行为学及足部形态;于模型制备前、制备后1、2和3周测定痛阈;于最后一次痛阈测定后3 d记录海马CA1区兴奋性突触后膜电位(EPSP),以高频刺激(HFS)诱发LTP。B1组于HFS前20min经腹腔注射荷包牡丹碱2 mg/kg,B2组于HFS后60 min给药。结果:与术前值比较,模型制备后三组各时点痛阈降低(P<0.05);与基础值比较,三组HFS后各时段EPSP幅值升高(P<0.05),组间比较差异无统计学意义(P>0.05)。结论:GABAA受体拮抗剂荷包牡丹碱不影响结扎L_(4,5)左侧脊神经所致神经病理性痛大鼠海马CA1区突触LTP的维持。

AIM： To investigate the effect of GABAA receptor on maintenance of synaptic long- term potentiation （LTP） in hippocampus in rats with neuropathic pain. METHODS： Eighteen adult male Wistar rats were randomly divided into 3 groups （n = 6）： neuropathic pain group （group NP）, bicuculine 1 group （ group B1 ） and bicuculine 2 group （group B2 ）. Neuropathic pain was produced by ligation of the left L4,s spinal nerve. The behav-iour of the rats was evaluated. The pain threshold was measured by electric stimulation at 7,14 and 21 d after surgery. The excitatory post-synaptic potential （EPSP） in hippocampal CA1 region was recorded at the third day after the last measurement of pain threshold. Changes in EPSP and LTP induced by high frequency stimulation （HFS） of the CA1 stratum radiatum of the rat hippocampus were ob- served using stereotaxic technology and extracellular recording respectively. Group B1 was administrated bicuculine （GABAA receptor antagonist） 2 mg/kg by i. p. 20 min before HFS, Group B2 received the same dose 60 rain after HFS. RESULTS：The pain threshold was significantly lower in 3 groups after surgery. The amplitudes of EPSP were significantly higher among 3 groups after HFS compared to base- line （ P 〈 0.05 ） , but there was no significant differ- ence in the amplitude of LTP among 3 groups （P 〉 0.05 ）. CONCLUSION： The results suggest that bicuculine of GABAA receptor antagonist might not affect synaptic LTP induction and maintenance in the CA1 area of the hippocampus of rats with the neuropathic pain by ligation of the left L4,5 spinal nerve.