He D Z, Evans B N, Dallos P
Department of Neurobiology and Physiology and Communication Sciences and Disorders, Northwestern University, Evanston, IL 60208.
Hear Res. 1994 Jul;78(1):77-90. doi: 10.1016/0378-5955(94)90046-9.
With the purpose of pinpointing the time of onset of electromotility, outer hair cells (OHCs) from apical and basal turns of the cochleae of postnatal gerbils, ranging in age from 6 to 19 days, were isolated and drawn into a glass microchamber. Length changes evoked by transcellular electrical stimulation were detected and measured with a photodiode detector. Motile responses first appeared in 3 out of 14 basal turn OHCs at 7 days after birth (DAB). At 8 DAB, 3 out of 13 apical turn cells also responded to the electrical stimulation. By 12 DAB, all the OHCs from both turns showed motile responses. Input-output functions relating applied stimulus and change in cell length revealed that the motile response threshold improved from 7 DAB to 12 DAB and the response amplitude kept increasing from 7 DAB until 13-14 DAB, when mature amplitudes were reached. Measurements of OHC length revealed only minor changes in basal turn hair cell length while apical hair cells continued to elongate until approximately 16 DAB. Since the onset of auditory function in gerbils occurs around 12 DAB and fine tuning develops between 14 and 17 DAB, our results suggest that the onset of OHC motility occurs earlier than that of auditory function and the maturation of the motility amplitude occurred earlier than the development of fine tuning. The maturation of OHC motility and the development of otoacoustic emissions are also compared and discussed.
为了确定电运动的起始时间，分离出6至19日龄新生沙鼠耳蜗顶回和底回的外毛细胞（OHC），并将其吸入玻璃微腔。通过光电二极管探测器检测并测量跨细胞电刺激引起的长度变化。出生后7天（DAB），14个底回OHC中有3个首次出现运动反应。出生后8天，13个顶回细胞中有3个也对电刺激产生反应。到出生后12天，两个回的所有OHC都表现出运动反应。将施加的刺激与细胞长度变化相关的输入-输出函数表明，运动反应阈值从出生后7天到12天有所改善，反应幅度从出生后7天到13 - 14天持续增加，直至达到成熟幅度。OHC长度测量显示，底回毛细胞长度仅有微小变化，而顶回毛细胞持续伸长直至约出生后16天。由于沙鼠听觉功能在出生后12天左右开始，精细调谐在14至17天之间发展，我们的结果表明，OHC运动起始早于听觉功能，运动幅度的成熟早于精细调谐的发展。还比较和讨论了OHC运动的成熟与耳声发射的发展。
