Kirita Takashi, Takebayashi Tsuneo, Mizuno Satoshi, Takeuchi Hirohito, Kobayashi Takeshi, Fukao Mitsuhiro, Yamashita Toshihiko, Tohse Noritsugu
Department of Orthopaedic Surgery, School of Medicine, Sapporo Medical University, Sapporo, Japan.
Spine (Phila Pa 1976). 2007 Jan 15;32(2):E65-72. doi: 10.1097/01.brs.0000252202.85377.96.
The DRG neuron was electrophysiologically investigated using a rat model with constriction of the proximal site of the DRG.
To investigate the pathomechanisms of lumbar radiculopathy, we established a rat model with constriction of the proximal site of the DRG. And to characterize the DRG neurons in the rat model of lumbar radiculopathy, the physiologic properties regarding action potential, Na, and K current of the DRG neurons were analyzed through the use of patch clamp recordings.
In lumbar root constriction models, properties of secondary afferent neurons in the dorsal horn have been investigated. However, the electrical properties of DRG neuron have not been well investigated.
To compare the excitability of DRG neurons between root constriction models and sham, we examined the threshold current, action potential (AP) threshold, resting membrane potential (RMP), afterhyperpolarization (AHP), action potential duration 50 (APD50), action potential amplitude, maximum rise time of AP, and pattern of discharges evoked by depolarizing current. We also examined the peak Na current and steady-state Na and K currents with the voltage clamp technique.
The rats in the root constriction group demonstrated mechanical allodynia and thermal hyperalgesia. In measurement of the action potential, lower threshold current, more depolarized RMP, larger AHP, and prolonged APD50 were measured in the root constriction neurons compared with the sham group. The incidence of sustained burst was significantly higher in root constriction neurons. The Na current in root constriction neurons was markedly larger. There were no significant differences in K current density and voltage dependency.
The constriction of lumbar root increased excitability and Na current amplitude of DRG neurons. These findings indicate that lumbar radicular pain may be associated with increased excitability of involved DRG neurons.
使用对背根神经节近端部位进行缩窄的大鼠模型，对背根神经节神经元进行电生理研究。
为研究腰椎神经根病的发病机制，我们建立了背根神经节近端部位缩窄的大鼠模型。为了描述腰椎神经根病大鼠模型中的背根神经节神经元特征，通过膜片钳记录分析了背根神经节神经元动作电位、钠电流和钾电流的生理特性。
在腰椎神经根缩窄模型中，已对背角二级传入神经元的特性进行了研究。然而，背根神经节神经元的电特性尚未得到充分研究。
为比较神经根缩窄模型与假手术组之间背根神经节神经元的兴奋性，我们检测了阈电流、动作电位（AP）阈值、静息膜电位（RMP）、超极化后电位（AHP）、动作电位持续时间50（APD50）、动作电位幅度、AP最大上升时间以及去极化电流诱发的放电模式。我们还使用电压钳技术检测了峰值钠电流以及稳态钠电流和钾电流。
神经根缩窄组大鼠表现出机械性异常性疼痛和热痛觉过敏。在动作电位测量中，与假手术组相比，神经根缩窄神经元的阈电流更低、RMP去极化程度更高、AHP更大且APD50延长。持续性爆发的发生率在神经根缩窄神经元中显著更高。神经根缩窄神经元中的钠电流明显更大。钾电流密度和电压依赖性无显著差异。
腰神经根缩窄增加了背根神经节神经元的兴奋性和钠电流幅度。这些发现表明，腰椎神经根性疼痛可能与受累背根神经节神经元兴奋性增加有关。
