Kruger L, Silverman J D, Mantyh P W, Sternini C, Brecha N C
Department of Anatomy, UCLA Center for Health Sciences 90024.
J Comp Neurol. 1989 Feb 8;280(2):291-302. doi: 10.1002/cne.902800210.
The distribution of calcitonin-gene-related peptide (CGRP) immunoreactivity (IR) was studied in peripheral tissues of rats. The ganglionic origin, somatosensory nature, and anatomic relations of this thin-axon population were evaluated with particular emphasis on possible nociceptive roles. In animals untreated with colchicine, CGRP-IR is found in a vast proportion of small- and medium-diameter sensory ganglion cells that give rise to numerous thinly myelinated and unmyelinated axons that display CGRP-IR throughout the body. The integumentary innervation consists, in part, of an extensive subpapillary network largely traced to dermal blood vessels, sweat glands, and "free" nerve endings, some of which are found within regions containing only mast cells, fibroblasts, and collagen. Dermal papillae contain CGRP-IR axons surrounding each vascular loop; other papillary axons end freely or occasionally surround Meissner corpuscles. Intraepithelial axons enter glabrous epidermal pegs, branching and exhibiting terminals throughout the stratum spinosum. A similar pattern is found in hairy skin with additional innervation entering the base and surrounding the lower third of each hair follicle, but apparently not supplying sebaceous glands and arrector pili muscle. Axons innervating nonkeratinized oral epithelium are similar or greater in number and distribution compared to epidermis, often with more extensive branching. The high density of intraepithelial CGRP-IR innervation does not appear to correlate with the sensitive mechanoreceptor-based increase in spatial sensory discriminative capacities in the distal portions of the limb. In deep somatic tissues, CGRP-IR is principally related to vasculature and motor end plates of striated muscle, but there is an extensive network of thin axons within bone, principally in the periosteum, and focally in joint capsules, but not in relation to muscle spindles or tendon organs. These findings, together with the distribution in cranial tissues described in an accompanying paper (Silverman and Kruger: J. Comp. Neurol. 280:303-330, '89), are considered in the context of a "noceffector" concept incorporating the efferent role of these sensory axons in various tissues. It is suggested that involvement in tissue maintenance and renewal during normal function, as well as following injury, may predominate over the relatively infrequent nociceptive role of this peptidergic sensory system.
研究了大鼠外周组织中降钙素基因相关肽（CGRP）免疫反应性（IR）的分布。评估了这群细轴突的神经节起源、躯体感觉性质和解剖关系，特别强调了其可能的伤害感受作用。在未用秋水仙碱处理的动物中，CGRP-IR存在于大部分中小直径感觉神经节细胞中，这些细胞发出许多薄髓鞘和无髓鞘轴突，这些轴突在全身都显示出CGRP-IR。皮肤神经支配部分由广泛的乳头下网络组成，该网络主要追溯到真皮血管、汗腺和“游离”神经末梢，其中一些位于仅含有肥大细胞、成纤维细胞和胶原的区域内。真皮乳头含有围绕每个血管袢的CGRP-IR轴突；其他乳头轴突自由终止或偶尔围绕梅克尔小体。上皮内轴突进入无毛表皮钉突，在棘层分支并显示终末。在有毛皮肤中也发现了类似的模式，另外有神经支配进入每个毛囊的基部并围绕其下三分之一，但显然不供应皮脂腺和立毛肌。支配非角化口腔上皮的轴突在数量和分布上与表皮相似或更多，通常分支更广泛。上皮内CGRP-IR神经支配的高密度似乎与基于敏感机械感受器的肢体远端空间感觉辨别能力的增加无关。在深部躯体组织中，CGRP-IR主要与横纹肌的血管系统和运动终板有关，但在骨内有一个广泛的细轴突网络，主要在骨膜中，在关节囊中局部存在，但与肌梭或腱器官无关。这些发现，连同随附论文（Silverman和Kruger：J. Comp. Neurol. 280:303 - 330, '89）中描述的在颅部组织中的分布，在一个“伤害效应器”概念的背景下进行了考量，该概念纳入了这些感觉轴突在各种组织中的传出作用。有人提出，在正常功能期间以及损伤后参与组织维持和更新可能比这个肽能感觉系统相对不常见的伤害感受作用更为突出。
