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

三叉神经损伤后常出现长时间的感觉异常和感觉迟钝，我们推测这些症状可能与三叉神经核的长期兴奋有关。因此，我们采用高速光学成像技术，观察了刺激初级传入纤维引起的三叉神经尾侧亚核（Vc）内神经元兴奋的传递和调制过程，并取小鼠或大鼠的延髓，用电压敏感性荧光染料RH 414对400 μm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备的荧光和差分荧光图像。每个切片的束直接通过单次电击或在100 s-1下的30个脉冲的序列刺激<-1>。无论是在矢状面或冠状面，膜兴奋诱发的单一刺激的道没有扩大在任何方向。在矢状面而不是冠状面观察到由单一刺激引起的边缘层或胶状质的更大传播。在水平切片上，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）。暴露于CNQX抑制了这些传播。高频刺激引起广泛传播和持久的膜去极化内的Mar，Mg和Magnocellularis区（Mar）。MK-801可抑制SG的去极化扩展。这些结果表明，水平切片适合于研究刺激三叉神经尾侧肌传入纤维引起的兴奋传播。此外，这些结果也支持谷氨酸也可能是三叉神经传入通路中的神经递质Vc。

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.