Thermal Detection Thresholds of Aδ- and C-Fibre Afferents Activated by Brief CO2 Laser Pulses Applied onto the Human Hairy Skin
Thermal Detection Thresholds of Aδ- and C-Fibre Afferents Activated by Brief CO2 Laser Pulses Applied onto the Human Hairy Skin
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DOI：
10.1371/journal.pone.0035817
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发表时间：
2012-04-25
期刊：
影响因子：
3.7
通讯作者：
Mouraux, Andre
中科院分区：
文献类型：
--
作者：
Churyukanov, Maxim;Plaghki, Leon;Mouraux, Andre
短暂的高功率激光脉冲施加到肢体远端的多毛皮肤上，产生与A δ和C纤维激活相关的双重感觉，称为第一和第二疼痛。然而，只有在避免A δ纤维的伴随激活的情况下，才能可靠地研究与C纤维的激活相关的神经生理学和行为反应。在此，使用一种新型的CO2激光刺激器，该激光刺激器能够通过在线测量目标部位的皮肤温度来反馈调节激光功率，并结合使用反应时间的自适应阶梯算法来区分由Δ纤维和C纤维输入触发的响应，我们表明，它是可能的估计鲁棒性和独立的热检测阈值的A δ纤维（46.9 +/-1.7摄氏度）和C-纤维（39.8 +/-1.7摄氏度）。此外，我们表明，这两个阈值是依赖于皮肤温度之前和/或周围的测试刺激，表明A δ和C纤维传入触发的行为反应，简短的激光脉冲的行为，至少部分地，作为检测器的皮肤温度的变化，而不是作为纯粹的水平检测器。最重要的是，我们的研究结果表明，A δ和C纤维传入激活的短暂的激光脉冲之间的阈值差异可以被利用来激活C纤维选择性和可靠的，提供的激光刺激器所产生的皮肤温度的上升是很好的控制。我们的方法可以构成一个工具，探索，在人类中，参与处理C-和A-δ纤维输入的生理和病理生理机制，分别。
Brief high-power laser pulses applied onto the hairy skin of the distal end of a limb generate a double sensation related to the activation of A delta- and C-fibres, referred to as first and second pain. However, neurophysiological and behavioural responses related to the activation of C-fibres can be studied reliably only if the concomitant activation of A delta- fibres is avoided. Here, using a novel CO2 laser stimulator able to deliver constant-temperature heat pulses through a feedback regulation of laser power by an online measurement of skin temperature at target site, combined with an adaptive staircase algorithm using reaction-time to distinguish between responses triggered by A delta- and C-fibre input, we show that it is possible to estimate robustly and independently the thermal detection thresholds of A delta- fibres (46.9 +/- 1.7 degrees C) and C-fibres (39.8 +/- 1.7 degrees C). Furthermore, we show that both thresholds are dependent on the skin temperature preceding and/or surrounding the test stimulus, indicating that the A delta- and C-fibre afferents triggering the behavioural responses to brief laser pulses behave, at least partially, as detectors of a change in skin temperature rather than as pure level detectors. Most importantly, our results show that the difference in threshold between A delta- and C-fibre afferents activated by brief laser pulses can be exploited to activate C-fibres selectively and reliably, provided that the rise in skin temperature generated by the laser stimulator is well-controlled. Our approach could constitute a tool to explore, in humans, the physiological and pathophysiological mechanisms involved in processing C-and A delta- fibre input, respectively.