Selective activation of primary afferent fibers evaluated by sine-wave electrical stimulation
Selective activation of primary afferent fibers evaluated by sine-wave electrical stimulation
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DOI：
10.1186/1744-8069-1-13
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发表时间：
2005-03-25
期刊：
影响因子：
3.3
通讯作者：
Yoshimura, Megumu
中科院分区：
文献类型：
--
作者：
Koga, Kohei;Furue, Hidemasa;Yoshimura, Megumu
频率为2000、250和5 Hz的经皮正弦波刺激（Neurometer）被认为分别选择性激活A β、A δ和C传入纤维。然而，很少有报道在细胞水平上测试这些刺激的选择性。在本研究中，我们分析了正弦波刺激施加到背根在急性分离的大鼠背根神经节（DRG）制备细胞内记录产生的动作电位（AP）。我们还测量了兴奋性突触反应引起的经皮刺激在脊髓背角的胶状质（SG）神经元，主要从C和Ad纤维，在体内膜片钳记录接收输入。在行为学研究中，在250和5 Hz刺激下观察到大鼠的逃跑或发声行为，其强度与0.8 mA（T5/T250）相似，而在2000 Hz刺激下，需要更高的强度（2.14 mA，T2000）。在DRG神经元中，通过2000 Hz刺激A β，通过250 Hz刺激A β和Ad，以及通过5 Hz刺激所有三类DRG神经元，在T5/T250产生AP。然而，由5 Hz刺激在A β和A δ中引起的AP频率远低于先前在生理条件下报道的AP频率。在体实验中，250和5 Hz刺激在T5/T250时在SG神经元中引起大幅度的EPSC。这些结果表明，2000 Hz刺激选择性地兴奋A β纤维，5 Hz刺激激活主要通过C纤维介导的伤害性传递。虽然250 Hz刺激激活Ad和A β纤维，但当同时产生疼痛感觉时，不会感知触觉。因此，250 Hz是激活Ad纤维引发伤害性感觉的有效刺激频率。因此，经皮正弦波刺激可以应用于通过比较阈值与三个刺激频率来评估感觉传递的功能变化。
Transcutaneous sine-wave stimuli at frequencies of 2000, 250 and 5 Hz (Neurometer) are thought to selectively activate A beta, A delta and C afferent fibers, respectively. However, there are few reports to test the selectivity of these stimuli at the cellular level. In the present study, we analyzed action potentials (APs) generated by sine-wave stimuli applied to the dorsal root in acutely isolated rat dorsal root ganglion (DRG) preparations using intracellular recordings. We also measured excitatory synaptic responses evoked by transcutaneous stimuli in substantia gelatinosa (SG) neurons of the spinal dorsal horn, which receive inputs predominantly from C and Ad fibers, using in vivo patch-clamp recordings. In behavioral studies, escape or vocalization behavior of rats was observed with both 250 and 5 Hz stimuli at intensity of similar to 0.8 mA (T5/T250), whereas with 2000 Hz stimulation, much higher intensity (2.14 mA, T2000) was required. In DRG neurons, APs were generated at T5/T250 by 2000 Hz stimulation in A beta, by 250 Hz stimulation both in A beta and Ad, and by 5 Hz stimulation in all three classes of DRG neurons. However, the AP frequencies elicited in A beta and A delta by 5 Hz stimulation were much less than those reported previously in physiological condition. With in vivo experiments large amplitude of EPSCs in SG neurons were elicited by 250 and 5 Hz stimuli at T5/T250. These results suggest that 2000 Hz stimulation excites selectively A beta fibers and 5 Hz stimulation activates noxious transmission mediated mainly through C fibers. Although 250 Hz stimulation activates both Ad and A beta fibers, tactile sensation would not be perceived when painful sensation is produced at the same time. Therefore, 250 Hz was effective stimulus frequency for activation of Ad fibers initiating noxious sensation. Thus, the transcutaneous sine-wave stimulation can be applied to evaluate functional changes of sensory transmission by comparing thresholds with the three stimulus frequencies.