Research of Neural Network in Spinal Dorsal Horn and Neuropathic Pain

在脊髓背角神经元中，膜电流对P物质（SP）的反应已经得到了很好的研究，但对降钙素基因相关肽（CGRP）和生长抑素（STT）的反应却知之甚少。因此，我们采用盲片钳技术在大鼠新鲜切片脊髓（3-4周）中解决了这些问题。在深层（III-VI）背角神经元（42/68个细胞）中，约60%的神经元在1 μM的SP溶液作用下呈现缓慢内向电流。这些电流被认为是通过G蛋白偶联SP受体引起的。这些神经元中的许多同时增加兴奋性突触后电流（EPSCs）。在CGRP （1μM）作用下，约30%（12/39）的深背角神经元向内呈现慢电流。在河蟹毒素（TTX, 1μ m）存在的情况下，观察到CGRP （n=1）缓慢向内电流，提示该电流是通过修复神经元上的G蛋白偶联CGRP受体引起的。对CGRP直接响应的神经元均表现为SP向内的慢电流，但CGRP向内的慢电流平均幅值小于SP向内的慢电流，而STT （1μM）的应用在约30%的补片深背角神经元（9/31细胞）中诱导了向外的慢电流。在河豚毒素（TTX, 1μ m）存在的情况下，STT （n=1）也观察到这种向外电流（数据未显示）。许多神经元还表现出SP向内的缓慢电流。STT的重复应用没有抑制缓慢的向外电流，尽管SP和CGRP向内的缓慢电流被脱敏。本研究提示，CGRP和STT，除了SP，在突触传递到深背角神经元中起重要作用。

Responses of membrane currents to substance P (SP) have well been examined in spinal dorsal horn neurons, but little is known about those to calcitonin gene-related peptide (CGRP) and somatostatin (STT). Therefore, we addressed these issues in freshly sliced spinal cord of rats (3-4 weeks) by using the blind patch clamp techniques.Of the dorsal horn neurons (42/68 cells) in the deep lamina (III-VI), about 60% showed the slow inward current by the bath application of SP (1 μM). These currents have been considered to be evoked though G protein-coupled SP receptors. Many of these neurons simultaneously increased excitatory post-synaptic currents (EPSCs). About 30% of deep dorsal horn neurons (12/39 cells) showed the slow inward current by the application of CGRP (1μM). The slow inward current by CGRP (n=1) was observed in the presence of tetrodotoxin (TTX, 1μM), suggesting that the currents are evoked though the G protein-coupled CGRP receptors on patched the neurons. The directly responsive neurons to CGRP always displayed the slow inward current by SP. However, the mean amplitude of these currents by CGRP was smaller than those by SP. On the other hand, the application of STT (1μM) induced the slow outward currents in about 30% of the patched deep dorsal horn neurons (9/31 cells). This outward current by STT (n=1) was also observed in the presence of tetrodotoxin (TTX, 1μM) (data not shown). Many these neurons also showed the slow inward current by SP. The slow outward currents were not suppressed by the repetitive application of STT, although the slow inward currents by SP and CGRP were desensitized.The present study suggests that CGRP and STT, in addition to SP, play important roles in synaptic transmission to deep dorsal horn neurons.