Westlund K N, Sun Y C, Sluka K A, Dougherty P M, Sorkin L S, Willis W D
Marine Biomedical Institute, University of Texas Medical Branch, Galveston 77550-2772.
Brain Res Brain Res Rev. 1992 Jan-Apr;17(1):15-27. doi: 10.1016/0165-0173(92)90003-5.
Glutamate and other excitatory amino acids have been shown to play a key role in nociception and the hyperalgesia associated with the acute inflammatory response. In an effort to understand more fully the role of Glu in this process, we determined that there is Glu in a percentage of axons in the medial articular nerve (MAN) of monkeys, a source of preterminal afferent fibers innervating the knee joint. After induction of the experimental knee joint inflammation with a kaolin/carrageenan mixture, comparison was made of the percentage of Glu positive axons in the MAN on the side of the inflammation versus the contralateral MAN using post-embedding immunogold electron microscopic methods. A doubling in the percentage of Glu-containing axons was observed on the side of the experimental arthritis as compared to the MAN of the other side or of uninjected controls. Glu positive axons were unmyelinated or were included in the small, thinly myelinated group in control nerves. Following induction of the inflammation, axonal diameter measurements revealed an increase in Glu content primarily in the small, thinly myelinated axons, which correspond to the group III afferent fibers. These increases were observed in the anesthetized preparation only when injection of kaolin/carrageenan was combined with joint flexion and mechanical stimulation. The dramatic increase in percentages of fibers stainable for Glu in the MAN following the induction of inflammation suggests that Glu content is greatly increased in the afferent fibers and may be a major contributor to the enhanced responses of sensory neurons in inflammatory states such as arthritis.
谷氨酸和其他兴奋性氨基酸已被证明在伤害感受以及与急性炎症反应相关的痛觉过敏中起关键作用。为了更全面地了解谷氨酸（Glu）在此过程中的作用，我们确定在猴子的内侧关节神经（MAN）中，一定比例的轴突中存在Glu，MAN是支配膝关节的终末前传入纤维的来源。在用高岭土/角叉菜胶混合物诱导实验性膝关节炎症后，使用包埋后免疫金电子显微镜方法，比较了炎症侧MAN中Glu阳性轴突的百分比与对侧MAN。与另一侧的MAN或未注射的对照相比，在实验性关节炎侧观察到含Glu轴突的百分比增加了一倍。在对照神经中，Glu阳性轴突无髓鞘或属于小的、薄髓鞘组。炎症诱导后，轴突直径测量显示Glu含量主要在小的、薄髓鞘轴突中增加，这些轴突对应于III组传入纤维。仅当注射高岭土/角叉菜胶与关节屈曲和机械刺激相结合时，在麻醉的制剂中才观察到这些增加。炎症诱导后MAN中可被Glu染色的纤维百分比的显著增加表明，传入纤维中的Glu含量大大增加，并且可能是关节炎等炎症状态下感觉神经元反应增强的主要促成因素。
