Smith D V, Klevitsky R, Akeson R A, Shipley M T
Department of Otolaryngology-Head and Neck Surgery, University of Cincinnati College of Medicine, Ohio 45267-0528.
J Comp Neurol. 1994 Sep 8;347(2):187-96. doi: 10.1002/cne.903470204.
Taste receptor cells are replaced throughout life, accompanied by continuing synaptogenesis between newly formed taste cells and first-order gustatory fibers. The neural cell adhesion molecule (NCAM) is expressed by a subset of taste cells in adult rodents and appears on gustatory nerve fibers during development prior to differentiation of the taste buds. We employed antibodies against the extracellular domain of the NCAM polypeptide (mAb 3F4) and against polysialic acid (PSA) residues found on embryonic forms of NCAM (mAb 5A5) to investigate the relationship between the expression of these molecules and the innervation of taste buds in adult rats. In unoperated rats, anti-NCAM recognized a subset of cells within the vallate taste buds and also the fibers of the glossopharyngeal (IXth) nerve, including those innervating the gustatory epithelium. Taste bud cells did not express PSA but mAb 5A5 immunoreactivity was observed on some fibers of the IXth nerve, including a few that entered the taste buds. Bilateral crush of the IXth nerve resulted in the loss of NCAM expression from the gustatory epithelium within 8 days. As IXth nerve fibers reinnervated the epithelium, NCAM expression was seen first in the nerve, followed by increased expression in the epithelium as the taste cells differentiated from their precursors. PSA expression by fibers of the IXth nerve did not return to normal until well after the regeneration of the vallate taste buds. The present results demonstrate that taste cell expression of NCAM is dependent upon innervation by the IXth nerve and that NCAM expression appears in the nerve prior to its expression in the differentiating epithelium during regeneration.(ABSTRACT TRUNCATED AT 250 WORDS)
味觉感受器细胞在整个生命过程中都会更新，同时新形成的味觉细胞与一级味觉纤维之间会持续发生突触形成。神经细胞黏附分子（NCAM）在成年啮齿动物的一部分味觉细胞中表达，并且在味蕾分化之前的发育过程中出现在味觉神经纤维上。我们使用针对NCAM多肽细胞外结构域的抗体（单克隆抗体3F4）和针对胚胎形式的NCAM上发现的多唾液酸（PSA）残基的抗体（单克隆抗体5A5），来研究这些分子的表达与成年大鼠味蕾神经支配之间的关系。在未手术的大鼠中，抗NCAM识别出轮廓乳头味蕾内的一部分细胞以及舌咽神经（第九对脑神经）的纤维，包括那些支配味觉上皮的纤维。味蕾细胞不表达PSA，但在第九对脑神经的一些纤维上观察到单克隆抗体5A5免疫反应性，包括一些进入味蕾的纤维。双侧切断第九对脑神经导致味觉上皮在8天内失去NCAM表达。随着第九对脑神经纤维重新支配上皮，NCAM表达首先在神经中出现，随后随着味觉细胞从前体细胞分化，上皮中的表达增加。直到轮廓乳头味蕾再生很久之后，第九对脑神经纤维的PSA表达才恢复正常。目前的结果表明，NCAM在味觉细胞中的表达依赖于第九对脑神经的神经支配，并且在再生过程中，NCAM在神经中的表达先于其在分化上皮中的表达出现。（摘要截短于250字）
