Kong W J, Hussl B, Thumfart W F, Schrott-Fischer A
Department of Otolaryngology, University Hospital of Innsbruck, Austria.
Hear Res. 1998 May;119(1-2):96-103. doi: 10.1016/s0378-5955(98)00033-1.
Acetylcholine (ACh) has long been considered a neurotransmitter candidate in the efferent vestibular system of mammals. Recently, choline acetyltransferase (ChAT), the synthesizing enzyme for ACh, was immunocytochemically localized in all five end-organs of the rat vestibule (Kong et al. (1994) Hear. Res. 75, 192-200). However, there is little information in the literature concerning the cholinergic innervation in the vestibular periphery of man. In the present study the ultrastructural localization of the ChAT-like immunoreactivity in the human vestibular periphery was investigated in order to reveal the cholinergic innervation in the human vestibular end-organs. A modified method of pre-embedding immunoelectron microscopy was applied. It was found that the ChAT-like immunoreactivity was located in the bouton-type vesiculated nerve terminals in the vestibular neurosensory epithelia of man. These ChAT-like immunostained nerve terminals make synaptic contacts either with afferent chalices surrounding type I vestibular sensory hair cells, or with type II vestibular sensory hair cells. These results show that the ChAT-like immunoreactivity in the human vestibular periphery is confined to the efferent vestibular system. The ChAT-containing efferents innervate both type I hair cells and type II hair cells, making postsynaptic and presynaptic contacts, respectively. This study presents evidence that ACh is a neurotransmitter candidate in the efferent vestibular system of man.
长期以来，乙酰胆碱（ACh）一直被认为是哺乳动物传出前庭系统中的一种神经递质候选物。最近，乙酰胆碱合成酶胆碱乙酰转移酶（ChAT）通过免疫细胞化学方法被定位在大鼠前庭的所有五个终器中（Kong等人，（1994年）《听觉研究》75卷，192 - 200页）。然而，文献中关于人类前庭外周胆碱能神经支配的信息很少。在本研究中，对人类前庭外周ChAT样免疫反应性的超微结构定位进行了研究，以揭示人类前庭终器中的胆碱能神经支配。应用了一种改良的包埋前免疫电子显微镜方法。结果发现，ChAT样免疫反应性位于人类前庭神经感觉上皮中的纽扣型囊泡化神经末梢中。这些ChAT样免疫染色的神经末梢与围绕I型前庭感觉毛细胞的传入杯状结构或与II型前庭感觉毛细胞形成突触联系。这些结果表明，人类前庭外周的ChAT样免疫反应性局限于传出前庭系统。含ChAT的传出纤维支配I型毛细胞和II型毛细胞，分别形成突触后和突触前联系。本研究提供了证据表明乙酰胆碱是人类传出前庭系统中的一种神经递质候选物。
