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Abstract：
The cutaneus trunci muscle (CTM) reflex produces a skin \"shrug\" in response to pinch on a rat\'s back through a three-part neural circuit: 1) A-fiber and C-fiber afferents in segmental dorsal cutaneous nerves (DCNs) from lumbar to cervical levels, 2) ascending propriospinal interneurons, and 3) the CTM motoneuron pool located at the cervicothoracic junction. We recorded neurograms from a CTM nerve branch in response to electrical stimulation. The pulse trains were delivered at multiple DCNs (T6-L1), on both sides of the midline, at two stimulus strengths (0.5 or 5 mA, to activate Aδ fibers or Aδ and C fibers, respectively) and four stimulation frequencies (1, 2, 5, or 10 Hz) for 20 s. We quantified both the temporal dynamics (i.e., latency, sensitization, habituation, and frequency dependence) and the spatial dynamics (spinal level) of the reflex. The evoked responses were time-windowed into Early, Mid, Late, and Ongoing phases, of which the Mid phase, between the Early (Aδ fiber mediated) and Late (C fiber mediated) phases, has not been previously identified. All phases of the response varied with stimulus strength, frequency, history, and DCN level/side stimulated. In addition, we observed nociceptive characteristics like C fiber-mediated sensitization (wind-up) and habituation. Finally, the range of latencies in the ipsilateral responses were not very large rostrocaudally, suggesting a myelinated neural path within the ipsilateral spinal cord for at least the A fiber-mediated Early-phase response. Overall, these results demonstrate that the CTM reflex shares the temporal dynamics in other nociceptive reflexes and exhibits spatial (segmental and lateral) dynamics not seen in those reflexes.NEW & NOTEWORTHY We have physiologically studied an intersegmental reflex exploring detailed temporal, stimulus strength-based, stimulation history-dependent, lateral and segmental quantification of the reflex responses to cutaneous nociceptive stimulations. We found several physiological features in this reflex pathway, e.g., wind-up, latency changes, and somatotopic differences. These physiological observations allow us to understand how the anatomy of this reflex may be organized. We have also identified a new phase of this reflex, termed the \"mid\" response.
摘要：
皮肤干肌肉（CTM）反射通过三部分神经回路对大鼠背部的挤压产生皮肤“耸肩”：1）节段背侧皮肤神经中的A纤维和C纤维传入（DCN）从腰椎到颈椎水平，2)上升的本体脊髓中间神经元，和3)位于颈胸交界处的CTM运动神经元池。我们记录了CTM神经分支响应电刺激的神经图。脉冲串在多个DCN(T6-L1)上传送，在中线的两边，在两个刺激强度(0.5或5mA，激活Aδ纤维或Aδ和C纤维，分别)和四个刺激频率(1、2、5或10Hz)持续20s。我们量化了时间动态(即，延迟，致敏,习惯,和频率依赖性）和反射的空间动力学（脊柱水平）。诱发的反应是时间窗口到早期，Mid,迟到,和正在进行的阶段，其中中期阶段，在早期(Aδ纤维介导的)和晚期(C纤维介导的)阶段之间，以前没有被识别。反应的所有阶段都随刺激强度而变化，频率,历史,和DCN水平/侧刺激。此外,我们观察到伤害性特征，如C纤维介导的致敏作用（结束）和习惯。最后,同侧反应的潜伏期范围不是很大，提示同侧脊髓内至少有A纤维介导的早期反应的有髓鞘神经通路。总的来说,这些结果表明，CTM反射在其他伤害性反射中共享时间动力学，并表现出在这些反射中未看到的空间（节段和横向）动力学。我们在生理上研究了一种节段间反射，探索详细的时间，以刺激强度为基础，刺激历史依赖性，对皮肤伤害性刺激的反射反应的侧向和分段量化。我们在这个反射通路中发现了几个生理特征,例如，结束,延迟更改，和体位差异。这些生理观察使我们能够理解这种反射的解剖结构是如何组织的。我们还发现了这种反射的新阶段，称为“中期”响应。
