Liberman M C, Simmons D D
J Acoust Soc Am. 1985 Jul;78(1 Pt 2):312-9. doi: 10.1121/1.392492.
Horseradish peroxidase (HRP) techniques have recently been applied to the study of the peripheral auditory system. These techniques make it possible to trace single, auditory-nerve fibers from their peripheral terminals on sensory cells to their central terminations within the cochlear nucleus. For the large, myelinated axons of type-I neurons contacting inner hair cells, HRP can be injected intracellularly through the same electrode used to record neural activity, allowing correlations to be made between structure and function on a single-cell basis. From these data, a cochlear frequency map has been constructed, and morphological correlates of differences in spontaneous discharge have been identified. For the small, unmyelinated axons of type-II neurons contacting outer hair cells, single-unit recordings have not yet been made; however, these neurons have been labeled by gross extracellular injections of HRP. Extracellular injections have also been used to study the peripheral terminations of single efferent neurons projecting to the outer hair cell region. The afferent fibers to the outer hair cell (OHC) region contact primarily OHCs from the third row, while efferent fibers primarily contact cells from the first row. Single efferent fibers innervate OHCs over a significantly larger cochlear length than single afferent fibers of either type. Possible functional interpretations of these morphological differences are discussed.
辣根过氧化物酶（HRP）技术最近已应用于外周听觉系统的研究。这些技术使得追踪单个听神经纤维成为可能，从它们在感觉细胞上的外周终末到它们在蜗神经核内的中枢终末。对于与内毛细胞接触的I型神经元的粗大、有髓轴突，HRP可以通过用于记录神经活动的同一电极进行细胞内注射，从而能够在单细胞基础上建立结构与功能之间的关联。根据这些数据，构建了耳蜗频率图，并确定了自发放电差异的形态学相关因素。对于与外毛细胞接触的II型神经元的细小、无髓轴突，尚未进行单单位记录；然而，这些神经元已通过HRP的大体细胞外注射进行了标记。细胞外注射也已用于研究投射到外毛细胞区域的单个传出神经元的外周终末。到外毛细胞（OHC）区域的传入纤维主要与第三排的OHC接触，而传出纤维主要与第一排的细胞接触。单个传出纤维支配OHC的耳蜗长度明显大于任何一种类型的单个传入纤维。文中讨论了这些形态学差异可能的功能解释。
