CNRS, IINS, UMR 5297, Université de Bordeaux, Neurocentre Magendie, 146 rue Leo-Saignat, 33077 Bordeaux cedex, France.
J Physiol. 2011 Jun 1;589(Pt 11):2733-43. doi: 10.1113/jphysiol.2011.207712. Epub 2011 Apr 11.
The dorsal horn of the spinal cord is the first central relay where nociceptive inputs are processed. Based on the expression and modulation of intrinsic electrophysiological properties in in vitro slice preparations, dorsal horn neurones (DHNs) display different discharge patterns (tonic, plateau or rhythmic), which shape the neurone's response to sensory inputs. However, it is unclear whether intrinsic properties play any role in sensory processing in vivo. Using in vivo patch clamp recordings in the adult rat, we here examine whether these intrinsic properties are present, and to what extent they determine the DHN response to natural stimulation. We focused primarily on wide dynamic range neurones in deep laminae. These cells displayed a multicomponent peripheral receptive field, comprising an excitatory firing zone, a low-probability firing fringe, and adjacent inhibitory zones. Deep DHNs presented similar intrinsic properties to those observed in vitro, including plateau potentials. These plateaus, underlying high frequency accelerating discharges and after-discharges, were triggered by mechanical stimulation of the excitatory receptive field. Persistent activities induced by activation of plateau potentials were interrupted by stimulation of peripheral inhibitory zones. Moreover, we show that plateau activation is necessary for the expression of windup in response to repetitive, nociceptive stimulation. Finally, using the spinal nerve ligation model of neuropathy, we demonstrate a significant increase in the proportion of plateau neurones in deep dorsal laminae. Our data, therefore, establish that intrinsic amplification properties are expressed within intact spinal circuits and suggest their involvement in neuropathy-induced hyperexcitability of deep DHNs.
脊髓背角是痛觉传入首先进行处理的中枢中继站。基于在体外切片制备中内在电生理特性的表达和调制，背角神经元（DHN）显示出不同的放电模式（紧张型、平台型或节律型），这些放电模式决定了神经元对感觉输入的反应。然而，内在特性是否在体内的感觉处理中起作用尚不清楚。本研究使用成年大鼠在体膜片钳记录，在此检查这些内在特性是否存在，以及它们在何种程度上决定了 DHN 对自然刺激的反应。我们主要关注于深部层中的宽动态范围神经元。这些细胞具有多成分的外周感受野，包括兴奋性放电区、低概率放电边缘和相邻的抑制区。深部 DHN 表现出与在体培养中观察到的相似的内在特性，包括平台电位。这些平台电位引发高频加速放电和后放电，由兴奋性感受野的机械刺激触发。由激活平台电位引起的持续活动被外周抑制区的刺激打断。此外，我们表明，平台电位的激活对于重复性伤害性刺激引起的 windup 的表达是必要的。最后，我们使用神经病理性的脊神经结扎模型，证明在深部背角中，平台神经元的比例显著增加。因此，我们的数据表明，内在的放大特性在完整的脊髓回路中得到表达，并提示其参与了神经病理性深 DHN 过度兴奋。
