离体脊髓运动神经元介导下行激活和外周传入的受体机制

目的:比较离体脊髓运动神经元(MN)介导下行激活和外周传入突触传递的受体机制。方法:应用新生大鼠(8~14d)脊髓切片MN细胞内记录技术,记录电刺激腹外侧索(VLF)和背根(DR)诱发的兴奋性突触后电位(EPSP)。结果:同侧VLF和DR刺激可对应诱发VLF-EPSP和DR-EPSP,与DR-EPSP相比,VLF-EPSP呈现潜伏期短、幅度高和上升快的特点,而且这一特征在用毕扣扣灵(30μmol/L)或印防己毒素(30μmol/L)和士的宁(1.0μmol/L)消除抑制性突触后电位的影响后(即纯的EPSP成分)持续存在。非NMDA受体阻断剂DNQX(1.0μmol/L)对纯的DR-EPSP和VLF-EPSP均有抑制作用,对两者快成分的抑制都较明显,而NMDA受体阻断剂AP5(30μmol/L)在抑制VLF-EP-SP和DR-EPSP时,对DR-EPSP的慢成分抑制更为显著。在5个MNs上可同时记录到同侧电刺激诱发的VLF-EP-SP、DR-EPSP及外源性谷氨酸反应。结论:在脊髓介导VLF的下行激活和外周传入的EPSP可能都是谷氨酸类递质,下行激活可能以非NMDA受体为主,而非-NMDA和NMDA受体在外周传入中均起重要作用,显示了明显的差异性。

Receptor mechanisms underlying synaptic responses of motoneurons to the descending activation and afferent input in neonatal rat spinal cord in vitro

Objective:To compare the receptor mechanisms underlying synaptic responses of motoneurons(MNs)to the descending activation and afferent input in neonatal rat spinal cord in vitro.Methods:The intracellular recordings were performed from MNs in neonate rat(8～14 days old)spinal cord slices and cell electrophysiological parameters of excitatory postsynaptic potential(EPSP)evoked by ventrolateral funiculus(VLF)and dorsal root(DR)stimulation were observed from the recorded MNs.Results:①EPSP evoked ipsilaterally by VLF and DR stimulation were observed from the same MNs(n=35).Compared with DR-EPSP,VLF-EPSP showed the characteristics of shorter latency,higher amplitude and faster rise,which persisted in the presence of bicuculline(30 μmol/L)or picrotoxin(30 μmol/L)and strychnine(1.0 μmol/L)(n=9).②VLF-EPSP(n=5)and DR-EPSP(n=5)were both sensitive to DNQX(1.0 μmol/L)and inhibited significantly(P<0.05)when pretreated by bicuculline or picrotoxin and strychnine.③AP5(30 μmol/L)could inhibit both VLF-EPSP(n=3)and DR-EPSP(n=3)in the presence of bicuculline or picrotoxin and strychnine while the amplitude of DR-EPSP were highly suppressed.Conclusion:The possible neurotransmitters mediating VLF-and DR-EPSP are excitatory amino acids.Non-NMDA receptors are critically involved in the synaptic transmissions of descending activation and both non-NMDA and NMDA are involved in afferent inputs.