Fundamental study on the mechanisms and treatments for paresthesia and dysesthesia following traumatic injury of trigeminal nerve

众所周知，三叉神经外伤性损伤有时伴随着长时间的感觉异常和感觉障碍，我们推测这些症状可能来自三叉神经核的长期兴奋。因此，利用高速光学成像技术，我们观察了刺激初级传入纤维诱发的三叉神经尾侧亚核(VC)伤害性传入传递和调制部位神经元兴奋的传播。取小鼠或大鼠的延髓，用电压敏感荧光染料RH414对400μm厚的冠状、矢状或水平切片进行染色。使用高速成像系统记录切片制剂的荧光和差分荧光图像。用单次电击或连续30次脉冲直接刺激每个脑片的肌束，刺激强度为100 S。无论是在矢状面还是在冠状面，单次刺激肌束所引起的膜兴奋并没有向任何方向扩展。在矢状面而不是冠状面，单次刺激诱发的神经元向边缘层或胶状质的扩散较大。在水平脑片中，由单次刺激引起的膜兴奋的传播从边缘层(MAR)扩展到胶状质(SG)。而暴露在CNQX中则抑制了这些传播。高频刺激在MAR区、MG区和巨细胞区(MAR)引起广泛而持久的膜去极化。MK-801可抑制SG的去极化效应。这些结果表明，水平切片适合于研究刺激三叉神经尾侧传入纤维引起的兴奋传播。此外，这些结果也支持谷氨酸可能也是三叉神经传入通路中的一种神经递质。

It is well known that traumatic injury of trigeminal nerve sometimes follows a long time paresthesia and dysesthesia and we hypothesized that these symptoms might come from the long-term excitation of trigeminal nucleus. Therefore, using high-speed optical imaging technique, we observed the propagation of neuronal excitation in the nociceptive afferent transmission and modulating site the trigeminal subnucleus caudalis (Vc), which was evoked by stimulation of primary afferent fibers.Medulla was removed from mice or rats, and coronal, sagittal or horizontal sectioned slices of 400 μm thicknesses were stained with a voltage-sensitive fluorescence dye RH414. Fluorescence and differential fluorescence images of a slice preparation were recorded using a high-speed imaging system. The tract of each slice was stimulated directly by single shock or a train of 30 pulses at 100 s^<-1>. Either in the sagittal or coronal slices, membrane excitation evoked by single stimulation of the tract did not expand in any directions. Larger propagations of evoked by the single stimulation to the marginal layer or substantia gelatinosa were observed in the sagittal rather than coronal slices. In contract, in the horizontal slices, propagations of membrane excitation, which were evoked by single stimulation, expanded from the Marginal layer (Mar) to the substantia gelatinosa (SG). And an exposure to CNQX suppressed these propagations. High frequency stimulation induced widely propagated and long-lasting membrane depolarizations within Mar, Mg and Magnocellularis area (Mar). Exposure to MK-801 suppressed the depolarization expansion to SG.These results suggest that horizontal slice is suitable for the study on the excitation propagation evoked by the afferent fiber stimulation within the trigeminal caudalis. Moreover, these results also support that glutamate might also be a neurotransmitter within the trigeminal afferent pathway in Vc.