Neuroscience Program, Stanford University, Stanford, CA.
Department of Molecular and Cellular Physiology, Stanford University, Stanford, CA.
J Gen Physiol. 2019 Oct 7;151(10):1213-1230. doi: 10.1085/jgp.201912374. Epub 2019 Sep 18.
Touch deforms, or strains, the skin beyond the immediate point of contact. The spatiotemporal nature of the touch-induced strain fields depend on the mechanical properties of the skin and the tissues below. Somatosensory neurons that sense touch branch out within the skin and rely on a set of mechano-electrical transduction channels distributed within their dendrites to detect mechanical stimuli. Here, we sought to understand how tissue mechanics shape touch-induced mechanical strain across the skin over time and how individual channels located in different regions of the strain field contribute to the overall touch response. We leveraged ' touch receptor neurons as a simple model amenable to in vivo whole-cell patch-clamp recording and an integrated experimental-computational approach to dissect the mechanisms underlying the spatial and temporal dynamics we observed. Consistent with the idea that strain is produced at a distance, we show that delivering strong stimuli outside the anatomical extent of the neuron is sufficient to evoke MRCs. The amplitude and kinetics of the MRCs depended on both stimulus displacement and speed. Finally, we found that the main factor responsible for touch sensitivity is the recruitment of progressively more distant channels by stronger stimuli, rather than modulation of channel open probability. This principle may generalize to somatosensory neurons with more complex morphologies.
触摸会使皮肤在接触点以外的区域变形或拉伸。触摸引起的应变场的时空性质取决于皮肤和下面组织的机械性能。感知触摸的感觉神经元在皮肤内分支，并依赖于分布在其树突内的一组机电转换通道来检测机械刺激。在这里，我们试图了解组织力学如何随时间在整个皮肤上塑造触摸引起的机械应变，以及位于应变场不同区域的单个通道如何有助于整体触摸反应。我们利用“触摸感受器神经元作为一个简单的模型，适用于体内全细胞膜片钳记录和综合实验计算方法，以剖析我们观察到的空间和时间动态背后的机制。与应变是在远处产生的观点一致，我们表明，在神经元的解剖范围之外施加强刺激足以引发 MRC。MRC 的幅度和动力学取决于刺激位移和速度。最后，我们发现，触摸灵敏度的主要因素是更强的刺激会招募越来越远的通道，而不是通道开放概率的调制。这一原则可能适用于具有更复杂形态的感觉神经元。
