Ackerley Rochelle, Wiklund Fernström Katarina, Backlund Wasling Helena, Watkins Roger H, Johnson Richard D, Vallbo Åke, Wessberg Johan
Aix Marseille Université, CNRS, LNSC (Laboratoire de Neurosciences Sensorielles et Cognitives - UMR 7260), Marseille , France.
Department of Physiology, University of Gothenburg , Gothenburg , Sweden.
J Neurophysiol. 2018 Oct 1;120(4):1885-1892. doi: 10.1152/jn.00940.2017. Epub 2018 Jul 25.
C-tactile (CT) afferents respond to gentle tactile stimulation, but only a handful of studies in humans and animals have investigated whether their firing is modified by temperature. We describe the effects of radiant thermal stimuli, and of stationary and very slowly moving mechanothermal stimuli, on CT afferent responses. We find that CT afferents are primarily mechanoreceptors, as they fired little during radiant thermal stimuli, but they exhibited different patterns of firing during combined mechano-cool stimulation compared with warming. CTs fired optimally to gentle, very slowly moving, or stationary mechanothermal stimuli delivered at neutral temperature (32°C, normal skin temperature), but they responded with fewer spikes (median 67% decrease) and at significantly lower rates (47% decrease) during warm (42°C) tactile stimuli. During cool tactile stimuli (18°C), their mean instantaneous firing frequency significantly decreased by 35%, but they often fired a barrage of afterdischarge spikes at a low frequency (5 Hz) that outlasted the mechanical stimulus. These effects were observed under a variety of stimulus conditions, including during stationary and slowly moving touch (0.1 cm/s), and we complemented these tactile approaches using a combined electrical-thermal stimulation experiment where we found a suppression of spiking during warming. Overall, CT afferents are exquisitely sensitive to tactile events, and we show that their firing is modulated with touch temperatures above and below neutral skin temperature. Warm touch consistently decreased their propensity to fire, whereas cool touch produced lower firing rates but afterdischarge spiking. NEW & NOTEWORTHY C-tactile (CT) afferents are thought to underpin pleasant touch, and previous work has shown that they respond optimally to a slow caress delivered at typical (neutral) skin temperature. Here, we show that, although CTs are primarily mechanoreceptive afferents, they are modified by temperature: warm touch decreases their firing, whereas cool touch produces lower firing rates but long-lasting spiking, frequently seen as afterdischarges. This has implications for the encoding of affective sensory events in human skin.
C类触觉（CT）传入神经对轻柔的触觉刺激有反应，但在人类和动物中只有少数研究调查了其放电是否会受到温度的影响。我们描述了辐射热刺激以及静态和非常缓慢移动的机械热刺激对CT传入神经反应的影响。我们发现CT传入神经主要是机械感受器，因为它们在辐射热刺激期间放电很少，但与温热刺激相比，它们在机械冷刺激组合期间表现出不同的放电模式。CT传入神经对在中性温度（约32°C，正常皮肤温度）下施加的轻柔、非常缓慢移动或静态的机械热刺激反应最佳，但在温暖（约42°C）触觉刺激期间，它们的放电尖峰减少（中位数减少67%）且放电频率显著降低（减少47%）。在冷触觉刺激（约18°C）期间，它们的平均瞬时放电频率显著降低35%，但它们经常在低频（约5Hz）下发出一连串的后放电尖峰，且后放电持续时间超过机械刺激。在各种刺激条件下都观察到了这些效应，包括在静态和缓慢移动的触摸（0.1cm/s）期间，并且我们通过电 - 热联合刺激实验补充了这些触觉方法，在该实验中我们发现升温期间放电尖峰受到抑制。总体而言，CT传入神经对触觉事件极其敏感，并且我们表明它们的放电会随着皮肤温度高于或低于中性皮肤温度而受到调节。温暖的触摸持续降低它们的放电倾向，而凉爽的触摸产生较低的放电频率但会出现后放电尖峰。新内容与值得注意之处：C类触觉（CT）传入神经被认为是愉悦触觉的基础，先前的研究表明它们对在典型（中性）皮肤温度下缓慢的抚摸反应最佳。在这里，我们表明，尽管CT传入神经主要是机械感受性传入神经，但它们会受到温度的影响：温暖的触摸会减少它们的放电，而凉爽的触摸会产生较低的放电频率但会出现持续时间长的尖峰放电，这种情况经常被视为后放电。这对人类皮肤中情感性感觉事件的编码具有重要意义。
