Research of Neural Network in Spinal Dorsal Horn and Neuropathic Pain

脊髓背角神经元膜电流对P物质(SP)的反应已被广泛研究，但对降钙素基因相关肽(CGRP)和生长抑素(STT)的反应知之甚少。因此，我们用盲膜片钳技术在新切开的大鼠脊髓(3-4周)上研究了这些问题。在深层(III-VI)的背角神经元(42/68个细胞)中，约60%的细胞在应用SP(1μM)时表现出缓慢的内向电流。这些电流被认为是通过G蛋白偶联的SP受体诱发的。其中许多神经元同时增加兴奋性突触后电流(EPSCs)。应用降钙素基因相关肽(1μM)后，约30%的背角深部神经元(12/39个细胞)出现慢内向电流。在河豚毒素(TTX，1μM)作用下，观察到1例降钙素基因相关肽(CGRP)慢内向电流，提示该电流是通过G蛋白偶联的降钙素基因相关肽受体介导的。降钙素基因相关肽的直接反应神经元总是表现为SP的慢内向电流。但CGRP对上述电流的平均幅度小于SP。另一方面，在贴片的背角深部神经元中，约30%(9/31个细胞)被应用短暂性T细胞(1μM)诱发出慢向外向电流。在河豚毒素(TTX，1μM)存在下，STT(n=1)的这种外向电流也被观察到(数据未显示)。许多神经元也表现出SP的慢内向电流。重复应用STT不能抑制慢向外向电流，但SP和CGRP引起的慢向内电流不敏感。本研究提示，除P物质外，CGRP和STT在突触传递至背角深层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.