The Hebrew University, Institute for Medical Research Israel Canada, Faculty of Medicine, Department of Medical Neurobiology, Jerusalem, IsraelbThe Hebrew University, The Edmond and Lily Safra Center for Brain Sciences, Jerusalem, Israel.
J Biomed Opt. 2017 Jul 1;22(7):76010. doi: 10.1117/1.JBO.22.7.076010.
Pain signals are detected by terminals of nociceptive peripheral fibers situated among the keratinocytes and epithelial cells. Despite being key structures for pain-related stimuli detection and transmission, little is known about the functional organization of terminals. This is mainly due to their minute size, rendering them largely inaccessible by conventional experimental approaches. Here, we report the implementation of an ultrafast optical recording approach for studying cultured neurite terminals, which are readily accessible for assay manipulations. Using this approach, we were able to study capsaicin-induced calcium and sodium dynamics in the nociceptive processes, at a near-action potential time resolution. The approach was sensitive enough to detect differences in latency, time-to-peak, and amplitude of capsaicin-induced ion transients along the terminal neurites. Using this approach, we found that capsaicin evokes distinctive calcium signals along the neurite. At the terminal, the signal was insensitive to voltage-gated sodium channel blockers, and showed slower kinetics and smaller signal amplitudes, compared with signals that were measured further up the neurite. These latter signals were mainly abolished by sodium channel blockers. We propose this ultrafast optical recording approach as a model for studying peripheral terminal signaling, forming a basis for studying pain mechanisms in normal and pathological states.
疼痛信号由位于角质细胞和上皮细胞之间的伤害性外周纤维末端检测到。尽管这些末端是检测和传递与疼痛相关刺激的关键结构，但对于它们的功能组织知之甚少。这主要是由于它们的微小尺寸，使得传统的实验方法很难接近它们。在这里，我们报告了一种超快光学记录方法的实施，用于研究培养的神经突末端，这些末端很容易进行测定操作。使用这种方法，我们能够在接近动作电位的时间分辨率下研究伤害性过程中辣椒素诱导的钙和钠动力学。该方法足够灵敏，可以检测到沿着末端神经突的辣椒素诱导的离子瞬变的潜伏期、到达峰值时间和幅度的差异。使用这种方法，我们发现辣椒素在神经突上诱导出独特的钙信号。在末端，信号对电压门控钠通道阻断剂不敏感，与在神经突上更远端测量的信号相比，其动力学较慢，信号幅度较小。这些后一种信号主要被钠通道阻断剂消除。我们提出这种超快光学记录方法作为研究外周末端信号的模型，为研究正常和病理状态下的疼痛机制奠定了基础。
