目的 探讨正常成年大鼠支配肌肉的外周伤害性感觉神经元的形态学和电生理特性。 方法 预先用荧光染料1,1’-dioctadecyl-3,3,3’,3’-tetrame-thylindocarbocyanine perchlorate（DiI，200 mg/L）标定背根神经节（DRG）中支配大鼠胫骨前肌的神经元，7～12 d后取材进行免疫组织化学染色或进行在体可视DRG电生理记录。结果 DiI逆行标记表明，支配大鼠胫骨前肌的初级感觉神经元主要集中在腰（L）3、L5 DRG上，DiI标记的阳性神经元胞体数量分别为19.8±7.1（L3）、26.5±8.0（L4）和14.2±5.0（L5）个（n=8），其中含大、中、小神经元。免疫组织化学结果表明，在L3~L5 背根神经节（DRG）DiI⁺（支配胫骨前肌）神经元中，降钙素基因相关肽（CGRP）（肽能）阳性神经元分别占31.5％、26.1％和22.3％；植物凝集素（IB4）（非肽能）阳性神经元分别占45.8％、45.1％和40.6％；表达瞬时受体电位通道香草醛亚型-1（TRPV1）的神经元分别占27.2％、26.3％和32.1％。电生理结果显示，对40mN以上机械刺激有反应的大部分为中、小神经元，引起其放电的外周机械刺激的阈值一般大于80mN（伤害性感觉神经元），外周感受野范围大，且位置多变。在测得外周轴突传导速度的神经元中，大部分（8/10）为C类［传导速度<1.5 m/s，平均机械阈值（124.6±40.5）mN］。 结论 大鼠L3~L5 DRG中支配胫骨前肌的伤害性感觉神经元多为中、小神经元，对于外界机械感受阈值较高，感受野范围较大，并且可表达多种痛觉神经元标志物。

Objective To investigate the morphological and electrophysiological characteristics of muscular nociceptive neurons in adult na?ve rats. Methods Fluorescent dye 1,1’-dioctadecyl-3,3,3’,3’-tetrame-thylindocarbocyanine perchlorate（Dil,200 mg/L）was injected into the right anterior tibialis muscle to label the primary muscular sensory neurons in the dorsal root ganglions (DRGs). Immunohistochemical staining and in vivo electrophysiological recordings of DRG neurons were conducted 7-12 days after injection. Results Primary sensory neurons innervating the anterior tibialis muscle (including small, medium and large sized somata) were mostly located in the lumbar(L)3, L4 and L5 DRGs (number of DiI⁺ neurons: 19.8±7.1, 26.5±8.0 and 14.2±5.0, respectively，n=8). Immunohistochemistry results showed that calcitonia gene related peptide (CGRP)+ (peptidergic) neurons innervating the anterior tibial muscle accounted for 31.5%, 26.1% and 22.3% of DiI⁺ neurons in L3, L4 and L5 DRG, respectively; while isolectin B4(IB4)+ (non-peptidergic) neurons accounted for 45.8%, 45.1% and 40.6% of DiI+ neurons in L3-L5 DRG, respectively. The transient receptor potential vanilloid type-1 (TRPV1)⁺ neurons accounted for 27.2%, 26.3%, and 32.1%, of DiI⁺ neurons in L3-L5 DRG, respectively. Electrophysiological recordings revealed that most of the neurons responding to 40mN or higher force mechanical stimulation were medium and small neurons. The mechanical threshold of nociceptive neurons is generally larger than 80mN (nociceptive sensory neurons), with large and variable peripheral receptive fields. Most of the neurons (8/10) with conduction velocity measured by electrically stimulating the sciatic nerve were C-nociceptive ［conduction velocity<1.5 m/s, average mechanical threshold (124.6±40.5) mN］. Conclusion Most of the primary nociceptive neurons innervating the anterior tibial muscle from L3-L5 DRGs in the rat are small-and medium-sized somata, with high mechanical threshold and large peripheral receptive field. In addition, these neurons may express a number of nociceptive neuronal markers.