Okazawa Makoto, Inoue Wataru, Hori Aiko, Hosokawa Hiroshi, Matsumura Kiyoshi, Kobayashi Shigeo
Division of Biological Information, Department of Intelligence Science and Technology, Graduate School of Informatics, Kyoto University, Kyoto 606-8501, Japan.
Neurosci Lett. 2004 Apr 8;359(1-2):33-6. doi: 10.1016/j.neulet.2004.01.074.
Noxious heat above approximately 45 degrees C applied on cold spots evokes a paradoxical cold sensation by activating cold fibers. It remains unresolved whether cold receptors respond to heat as well, or whether noxious-heat receptors and cold receptors coexist in the same fiber. Recently, noxious heat receptors (TRPV1) and cold receptors (TRPM8) have been cloned. It is controversial, however, whether TRPV1 and TRPM8 coexist in the same sensory neuron. Here, we investigate colocalization of these receptors in dorsal root ganglion (DRG) of rats. TRPV1 was expressed in 29% of TRPM8-positive cells in DRG sections. In Ca2+ imaging, noxious heat excited many of the cold-sensitive cells in culture. In a whole-cell current-clamp mode, noxious heat, capsaicin, cooling and menthol all evoked receptor potentials and impulses in a subset of DRG neurons. This colocalization of TRPV1 and TRPM8 in a DRG neuron may be the basis for the paradoxical cold sensation.
施加在冷点上约45摄氏度以上的有害热通过激活冷纤维引发一种矛盾的冷觉。冷感受器是否也对热有反应，或者有害热感受器和冷感受器是否共存于同一纤维中，这仍未得到解决。最近，有害热感受器（TRPV1）和冷感受器（TRPM8）已被克隆。然而，TRPV1和TRPM8是否共存于同一感觉神经元存在争议。在此，我们研究这些感受器在大鼠背根神经节（DRG）中的共定位情况。在DRG切片中，TRPV1在29%的TRPM8阳性细胞中表达。在钙离子成像中，有害热激发了培养物中许多冷敏细胞。在全细胞膜片钳电流钳模式下，有害热、辣椒素、冷却和薄荷醇均在一部分DRG神经元中引发了感受器电位和冲动。TRPV1和TRPM8在DRG神经元中的这种共定位可能是矛盾冷觉的基础。
