Lambertz D, Hoheisel U, Mense S
Institute of Anatomy and Cell Biology, University Heidelberg, Im Neuenheimer Feld 307, D-69120 Heidelberg, Germany.
Neurosci Lett. 2006 Nov 27;409(1):14-8. doi: 10.1016/j.neulet.2006.09.016. Epub 2006 Oct 10.
Previous results from our group and others showed that skin and muscle afferents are equipped with tetrodotoxin-resistant (TTX-r) channels. The great majority of the TTX-r fibres are unmyelinated (C or group IV) and are assumed to have nociceptive functions. Therefore, a block of the TTX-sensitive (TTX-s) fibres offers the possibility to study reactions of central nervous neurones to a purely nociceptive input. The present study compared spinal synaptic field potentials (SFPs) evoked by electrical stimulation of TTX-r afferent fibres from skin and muscle at various depths of the spinal segments L4 and L5 in the rat. Cutaneous input was produced by stimulation of the sural nerve (SU), input from muscle by stimulation of the gastrocnemius-soleus nerves (GS). To block the (non-nociceptive) TTX-s afferents, a pool containing TTX (concentration 1microM) was built around the dorsal roots L3-L6. As a measure of synaptic activity, the area of averaged SFPs was determined. After TTX application, the SFPs of fast conducting myelinated afferent fibres vanished completely. Simultaneously, the size of the potentials evoked by electrical stimulation of slowly conducting TTX-r skin and muscle afferents increased significantly. The field potentials of TTX-r GS afferents had a maximum in laminae IV-VI of the dorsal horn, whereas the SFPs induced by SU stimulation were more evenly distributed over all laminae. The results are a further indication that nociceptive input from skin and muscle is differently processed at the spinal level.
我们团队及其他团队之前的研究结果表明，皮肤和肌肉传入神经配备有河豚毒素抗性（TTX-r）通道。绝大多数TTX-r纤维是无髓鞘的（C类或IV组），并被认为具有伤害感受功能。因此，阻断河豚毒素敏感（TTX-s）纤维为研究中枢神经神经元对纯伤害性输入的反应提供了可能性。本研究比较了在大鼠L4和L5脊髓节段不同深度处，电刺激皮肤和肌肉的TTX-r传入纤维所诱发的脊髓突触场电位（SFP）。通过刺激腓肠神经（SU）产生皮肤输入，通过刺激腓肠肌-比目鱼肌神经（GS）产生肌肉输入。为了阻断（非伤害性的）TTX-s传入神经，在L3-L6背根周围构建了一个含有TTX（浓度为1微摩尔）的池。作为突触活动的一种测量方法，测定了平均SFP的面积。应用TTX后，快速传导的有髓鞘传入纤维的SFP完全消失。同时，电刺激缓慢传导的TTX-r皮肤和肌肉传入神经所诱发的电位大小显著增加。TTX-r GS传入神经的场电位在背角的IV-VI层达到最大值，而SU刺激所诱发的SFP在所有层中分布更为均匀。这些结果进一步表明，皮肤和肌肉的伤害性输入在脊髓水平的处理方式不同。
