Generator potentials and spike initiation in auditory fibers of goldfish.
Generator potentials and spike initiation in auditory fibers of goldfish.
复制标题
金鱼听觉纤维的发生器电位和尖峰启动。
作者：
I. Kyogoku;S. Matsuura;M. Kuno
从金鱼球囊的单个小传入纤维，即S2纤维，记录细胞外或细胞内的反应，以阐明这些纤维中的自发和声诱发放电是如何从产生电位开始的。从5条金鱼的球囊神经中随机选取78个单位，根据棘间距变异系数(CV)将其分为不规则型(59个单位，CV>0.3)、中间型(10个单位)和规则型(9个单位，CV<0.23)。不规则型自发活动表现为突发性放电(38个单位)或随机放电(21个单位)。在每个声波都可以记录到清晰的发生器电位的情况下，在没有刺激声的情况下，也可以观察到自发的发电机电位。这些自发电位在幅度和时间进程上都是不规则的，而且往往含有比声诱发诱发电位慢得多的成分。S2纤维的声诱发诱发电位在每次声波后产生0.4-0.85ms的延迟，其时程与大的S1纤维的兴奋性突触后电位(EPSP)相当。他们还分享了其他特性，如幅度的适应性下降，递增和递减的反应，以及关闭抑制。S2纤维的声诱发诱发电位的平均幅度与传入放电频率呈线性关系。自发性诱发电位和声诱发诱发电位的动作电位阈值幅度无明显差异。推测S_2纤维自发和声诱发放电的产生电位是由毛细胞释放递质产生的。
Responses were recorded extra- or intracellularly from single, small afferent fibers of the goldfish saccule, that is, S2 fibers, to clarify how the spontaneous and sound-evoked firings in these fibers are initiated from generator potentials. Spontaneously active units randomly selected from the saccular nerve of five goldfish (total 78 units) were classified by the coefficient of variation (CV) of interspike intervals into irregular (59 units; CV greater than 0.3), intermediate (10 units), and regular types (9 units; CV less than 0.23). The irregular type showed a burst (38 units) or random (21 units) pattern of firing in spontaneous activity. In cases where a clear generator potential could be recorded in response to each sound wave, spontaneous generator potentials could also be observed in the absence of stimulus sound. These spontaneous potentials were irregular in amplitude and time course, and often contained components much slower than the sound-evoked generator potentials. The sound-evoked generator potentials in S2 fibers were produced with a delay of 0.4-0.85 ms following each sound wave, and had a time course comparable to the sound-evoked excitatory postsynaptic potentials (EPSPs) of large S1 fibers. They also shared other properties such as adaptive decline in amplitude, incremental and decremental responses, and off-suppression. The mean amplitude of the sound-evoked generator potentials in S2 fibers was linearly related to the rate of afferent firing. There was no apparent difference in the action potential threshold amplitude for spontaneous and sound-evoked generator potentials. It may be concluded that the generator potentials that underlie the spontaneous and sound-evoked firing of S2 fibers are produced by the release of transmitter by hair cells.