Kobayashi Kimiko, Fukuoka Tetsuo, Obata Koichi, Yamanaka Hiroki, Dai Yi, Tokunaga Atsushi, Noguchi Koichi
Department of Anatomy and Neuroscience, Hyogo College of Medicine, Hyogo 663-8501, Japan.
J Comp Neurol. 2005 Dec 26;493(4):596-606. doi: 10.1002/cne.20794.
The transient receptor potential (TRP) superfamily of cation channels contains four temperature-sensitive channels, named TRPV1-4, that are activated by heat stimuli from warm to that in the noxious range. Recently, two other members of this superfamily, TRPA1 and TRPM8, have been cloned and characterized as possible candidates for cold transducers in primary afferent neurons. Using in situ hybridization histochemistry and immunohistochemistry, we characterized the precise distribution of TRPA1, TRPM8, and TRPV1 mRNAs in the rat dorsal root ganglion (DRG) and trigeminal ganglion (TG) neurons. In the DRG, TRPM8 mRNA was not expressed in the TRPV1-expressing neuronal population, whereas TRPA1 mRNA was only seen in some neurons in this population. Both A-fiber and C-fiber neurons expressed TRPM8, whereas TRPV1 was almost exclusively seen in C-fiber neurons. All TRPM8-expressing neurons also expressed TrkA, whereas the expression of TRPV1 and TRPA1 was independent of TrkA expression. None of these three TRP channels were coexpressed with TrkB or TrkC. The TRPM8-expressing neurons were more abundant in the TG compared with the DRG, especially in the mandibular nerve region innervating the tongue. Our data suggest heterogeneity of TRPM8 and TRPA1 expression by subpopulations of primary afferent neurons, which may result in the difference of cold-sensitive primary afferent neurons in sensitivity to chemicals such as menthol and capsaicin and nerve growth factor.
瞬时受体电位（TRP）阳离子通道超家族包含四个对温度敏感的通道，命名为TRPV1 - 4，它们可被从温暖到有害范围的热刺激激活。最近，该超家族的另外两个成员TRPA1和TRPM8已被克隆，并被鉴定为初级传入神经元中冷感受器的可能候选者。我们使用原位杂交组织化学和免疫组织化学方法，对TRPA1、TRPM8和TRPV1 mRNA在大鼠背根神经节（DRG）和三叉神经节（TG）神经元中的精确分布进行了表征。在DRG中，TRPM8 mRNA在表达TRPV1的神经元群体中不表达，而TRPA1 mRNA仅在该群体的一些神经元中可见。A纤维和C纤维神经元均表达TRPM8，而TRPV1几乎仅见于C纤维神经元。所有表达TRPM8的神经元也表达TrkA，而TRPV1和TRPA1的表达与TrkA表达无关。这三种TRP通道均不与TrkB或TrkC共表达。与DRG相比，TG中表达TRPM8的神经元更为丰富，尤其是在支配舌头的下颌神经区域。我们的数据表明初级传入神经元亚群对TRPM8和TRPA1的表达存在异质性，这可能导致冷敏初级传入神经元对薄荷醇、辣椒素和神经生长因子等化学物质的敏感性存在差异。
