THE ROLE OF TETRODOTOXIN-RESISTANT SODIUM-CHANNELS OF SMALL PRIMARY AFFERENT-FIBERS
THE ROLE OF TETRODOTOXIN-RESISTANT SODIUM-CHANNELS OF SMALL PRIMARY AFFERENT-FIBERS
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DOI：
10.1016/0006-8993(94)91772-8
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发表时间：
1994-03-07
期刊：
影响因子：
2.9
通讯作者：
JEFTINIJA, S
中科院分区：
文献类型：
--
作者：
JEFTINIJA, S
在体外脊髓-背根神经节制备物中，使用背根神经节 (DRG) 和背角 (DH) 神经元的细胞内记录来研究抗河豚毒素 (TTX-R) 传入纤维在浅表 DH 感觉突触传递中的作用。在 DRG 中加入 25-50 mM 钾可使 DRG 神经元去极化，阻断大神经元的动作电位，诱发慢传导神经元的动作电位，并兴奋突触背角神经元。通过电刺激大的有髓神经纤维在 DH 神经元中诱发兴奋性突触后电位 (EPSP)，但不是通过刺激小的无髓神经纤维诱发的兴奋性突触后电位 (EPSP) 被初级传入细胞的钾处理所阻断。当河豚毒素作用于感觉神经元时，消除了快纤维中的动作电位，但对慢传导传入神经群中的动作电位没有影响。 TTX 的外周应用阻断了电刺激诱发的快速 EPSP，但未能阻断电诱发的慢 EPSP 以及对感觉神经元施加高钾诱导的 DH 神经元突触激活。此外，在大多数神经元中，高钾会增强电诱发的 TTX 抗性 EPSP。这种效应在无 Na+ 的溶液中被消除。这些发现表明，应用于 DRG、背根和外周突的高 [K+](e) 选择性激活 DH 的初级传入输入，该输入是钠依赖性的且具有河鲀毒素抗性。
Intracellular recordings from neurons in the dorsal root ganglion (DRG) and dorsal horn (DH), in an in vitro spinal cord-dorsal root ganglion preparation, were used to investigate the role of tetrodotoxin-resistant (TTX-R) afferent fibers in the sensory synaptic transmission in the superficial DH. Bath application of 25-50 mM potassium to the DRG depolarized the DRG neurons, blocked action potentials in the large neurons, evoked action potentials in slow conducting neurons, and synaptically excited dorsal horn neurons. Excitatory postsynaptic potentials (EPSP) which were evoked in DH neurons by electrical stimulation of large myelinated fibers, but not those evoked by stimulation of small unmyelinated fibers, were blocked by the potassium treatment of the primary afferents. Tetrodotoxin, when applied to the sensory neurons, abolished the action potentials in fast fibers but had no effect on the action potentials in a population of slow conducting afferents. Peripheral application of TTX blocked the fast EPSPs evoked by electrical stimulation but failed to block the electrically evoked slow EPSPs and the synaptic activation of DH neurons induced by the application of high potassium to sensory neurons. Furthermore, high potassium potentiated electrically evoked, TTX-resistant EPSPs in the majority of neurons. This effect was abolished in Na+-free solution. These findings indicate that high [K+](e) applied to the DRG, dorsal root and peripheral process selectively activates a primary afferent input to the DH, which is sodium-dependent and tetrodotoxin resistant.