对侧腹外侧索电刺激在新生大鼠脊髓切片运动神经元诱发的突触反应

目的:探讨对侧腹外侧索(cVLF)下行激活对离体脊髓运动神经元(MN)活动的突触调制作用。方法:应用新生大鼠(8~14 d)脊髓切片MN细胞内记录技术,观察cVLF或同侧VLF(iVLF)电刺激在MN所诱发的突触反应。结果:在32个测试的MNs,观察到cVLF电刺激可在21个MNs上诱发去极化反应(即cVLF性兴奋性突触后电位,cVLF-EPSP),在1个MN上诱发超极化反应(即cVLF性抑制性突触后电位,cVLF-IPSP),在4个MNs上诱发cVLF-EPSP后复合有cVLF-IPSP的反应。cVLF-EPSP具有刺激强度依赖性、被低钙高镁溶液取消的特性,与i VLF性EPSP相比,有潜伏期较长的特点(P<0.001)。cVLF-IPSP呈膜电位依赖性,并被印防己毒素(30μmol/L)及士的宁(1.0μmol/L)取消。结论:cVLF的下行激活可通过兴奋性和抑制性突触传递调制MN的活动,其cVLF-IPSP可能由γ-氨基丁酸A受体和(或)甘氨酸受体介导。

Synaptic responses of motoneurons evoked by contralateral ventrolateral funiculus stimulation in neonatal rat spinal cord slices

Objective:To evaluate the modulation of motoneurons(MNs) by contralateral descending activation in neonatal rat spinal cord slices.Methods: The intracellular recordings were performed in MNs of spinal cord slices isolated from neonatal rats(8～14 days old),and contralateral ventrolateral funiculus(cVLF) or ipsilateral VLF(iVLF) stimulation was applied to activate the descending fibers.Results: Among 32 tested MNs,depolarizing responses(excitatory postsynaptic potential,EPSP) were elicited by cVLF stimulation(cVLF-EPSP) in 21 MNs,hyperpolarizing response(inhibitory postsynaptic potential,IPSP) in 1 MN,and IPSP preceded by EPSP in 4 MNs.The cVLF-EPSPs were stimulus intensity-dependent,and could be abolished by low Ca2+/high Mg2+solution.Compared with iVLF-EPSPs, cVLF-EPSPs showed longer latency(P<0.001).The cVLF-IPSP presented with membrane potential-dependent property and was eliminated by the perfusion of picrotoxin(30 μmol/L) and strychnine(1.0 μmol/L).Conclusion: The findings suggest that the contralateral descending activation in VLF may modulate the activities of MNs in neonatal rat spinal cord slices by excitatory or inhibitory synaptic transmission,and the cVLF-IPSP may be mediated by GABAA receptor and/or glycine recep-tor.