Plasticity and in Spinal Dorsal Horn Neuron and Neuropathic Pain : An Analysis by Patch Clamp Recordings

神经递质和调节剂在脊髓背角浅层神经元中的作用已被充分研究，但对深层背角神经元中的神经递质和调节剂的作用知之甚少。我们以前的研究表明，SP、CGRP和生长抑素在突触传递到背角深部神经元中起重要作用。本研究采用大鼠新鲜脊髓切片盲法膜片钳技术，观察了大鼠(3~4周)脊髓内SP和Menk对深部背角神经元的反应。用SP(1μM)浸浴1min，约有60%的深板层(III-V)背角深部神经元出现大于5pA的慢内向电流。这些电流被认为是通过G蛋白偶联的SP受体在修补的细胞上被诱发的。部分记录到的神经元增加了自发性EPSCs和/或IPSCs的数目和波幅。而在Menk(5μM)、DAMGO(Mu受体激动剂)的作用下，约有60%的深背角神经元显示出大于5pA的慢向外向电流。1μM)或DADLE(增量受体激动剂；1μM)1分钟。这些电流也被认为是通过G蛋白偶联的Mu/Delta受体在修补的细胞上被诱发的。对Menk反应的神经元总是表现出DAMGO、DADLE或两者兼有的外向电流。重复应用Menk不能抑制外向电流的幅度。大多数SP引起慢内向电流的深背角神经元在脑啡肽、DAMGO或DADLE作用下表现为慢向外电流，反之亦然。本研究表明，约60%的深背角神经元既通过NK1受体接受兴奋性传入，又通过Mu/Delta受体接受抑制性传入。

The actions of neurotransmitters and modulators have well been investigated in superficial spinal dorsal horn neurons, but little is known about those in deep dorsal horn neurons. Our previous studies suggested that SP, CGRP and somatostatin play important roles in synaptic transmission to deep dorsal horn neurons. In this study, responses of SP and mENK to deep dorsal horn neurons were examined by the blind patch clamp technique used freshly sliced spinal cord of the rat (3-4weeks). About 60% of deep dorsal horn neurons in the deep lamina (III-V) showed the slow inward currents more than 5 pA by the bath application of SP (1 μM) for 1 min. These currents are considered to be evoked though G protein-Coupled SP receptors on the patched cells. Some of the recorded neurons enhanced the number and the peak amplitude of spontaneous EPSCs and/or IPSCs by the application SP. On the other hand, about 60% of the deep dorsal horn neurons showed the slow outward currents more than 5 pA by the bath application of mENK (5 μM), DAMGO (mu-receptor agonist. 1 μM), or DADLE (delta-receptor agonist; 1 μM) for 1 min. These currents are also considered to be evoked though G protein-coupled mu/delta-receptors on the patched cells. The responsive neurons to mENK always displayed the outward current by DAMGO, DADLE, or both. The amplitude of outward current was not suppressed by the repetitive application of mENK. Most of deep dorsal horn neurons with the slow inward currents by SP showed the slow outward currents by enkephalin, DAMGO, or DADLE, and vice versa. The present study suggests that about 60% of deep dorsal horn neurons receive both excitatory inputs though the NK1 receptors and inhibitory inputs though the mu-/delta-receptors.