McMullan Simon, Simpson Daniel A A, Lumb Bridget M
Department of Physiology, School of Medical Sciences, University of Bristol, University Walk, Bristol BS8 1TD, UK.
J Neurosci Methods. 2004 Sep 30;138(1-2):133-9. doi: 10.1016/j.jneumeth.2004.03.020.
There is strong evidence that A- and C-fibre nociceptors evoke significantly different sensory experiences, are differentially sensitive to pharmacological intervention, and play different roles in pain pathology. It is therefore of considerable interest to be able to selectively activate one fibre type or the other in studies of nociceptive processing. Here, we report significant modifications to a non-invasive technique, first described by Yeomans et al. [Pain 59 (1994) 85; Pain 68 (1996) 141; Pain 68 (1996) 133], which uses different rates of skin heating to preferentially activate A- or C-nociceptors. A copper disk (diameter: 4mm) was used to transfer heat evenly across the dorsal surface of the rat hindpaw. Initial experiments established the relationship between the temperature at the skin surface and the sub-epidermal temperature. Subsequently, the vanilloid capsaicin, which sensitises unmyelinated C-mechanoheat nociceptors, was shown to decrease the thresholds of reflex responses evoked by slow rates of heating. In contrast thresholds of responses to fast rates of skin heating were unchanged, indicating that nociceptors activated by this stimulus were capsaicin-insensitive A-fibre heat nociceptors.
有强有力的证据表明，A 类和 C 类纤维伤害感受器会引发显著不同的感觉体验，对药物干预的敏感性不同，并且在疼痛病理过程中发挥不同作用。因此，在伤害性感受处理的研究中能够选择性地激活一种纤维类型或另一种纤维类型，具有相当大的研究意义。在此，我们报告了对一种非侵入性技术的重大改进，该技术最初由Yeomans等人描述[《疼痛》59(1994)85；《疼痛》68(1996)141；《疼痛》68(1996)133]，该技术利用不同的皮肤加热速率来优先激活 A 类或 C 类伤害感受器。使用一个铜盘(直径:4 毫米)在大鼠后爪的背表面均匀传递热量。最初的实验确定了皮肤表面温度与表皮下温度之间的关系。随后，研究表明，能使无髓鞘 C 类机械热伤害感受器敏感化的香草酸辣椒素会降低慢速加热引发的反射反应阈值。相比之下，对快速皮肤加热的反应阈值没有变化，这表明被这种刺激激活的伤害感受器是对辣椒素不敏感的 A 类纤维热伤害感受器。
