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浅层背角神经元中的作用已被研究得很好，但对深层背角神经元的作用知之甚少。我们前期的研究表明SP、CGRP和生长抑素在突触传递到深背角神经元中起重要作用。本研究采用大鼠脊髓切片（3-4周），采用盲膜片钳技术检测SP和mENK对大鼠深背角神经元的反应。SP （1 μM）浸泡1 min后，约60%的深背角神经元（III-V）表现出大于5 pA的缓慢内向电流。这些电流被认为是通过修补细胞上的G蛋白偶联SP受体引起的。部分神经元自发性EPSCs和/或IPSCs的数量和峰值振幅在SP的作用下有所增加。另一方面，约60%的深背角神经元在5 μM （mENK）、DAMGO （mu受体激动剂）的作用下显示出大于5 pA的缓慢外向电流。1 μM)，或DADLE （δ受体激动剂，1 μM）作用1分钟。这些电流也被认为是通过修补细胞上的G蛋白偶联mu/delta受体引起的。对mENK有反应的神经元总是通过DAMGO、DADLE或两者同时显示向外电流。反复施加mENK不抑制向外电流的幅值。SP向内电流缓慢的深背角神经元，大部分表现为脑啡肽、DAMGO或DADLE向外电流缓慢，反之亦然。目前的研究表明，约60%的深背角神经元既通过NK1受体接受兴奋性输入，也通过mu-/delta受体接受抑制性输入。

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.