Department of Biology and Neuroscience Program, Amherst College, Amherst, MA, 01002, USA.
Department of Mathematics and Statistics, Smith College, Northampton, MA, 01063, USA.
Sci Rep. 2018 Oct 5;8(1):14851. doi: 10.1038/s41598-018-33064-z.
Without stimuli, hair cells spontaneously release neurotransmitter leading to spontaneous generation of action potentials (spikes) in innervating afferent neurons. We analyzed spontaneous spike patterns recorded from the lateral line of zebrafish and found that distributions of interspike intervals (ISIs) either have an exponential shape or an "L" shape that is characterized by a sharp decay but wide tail. ISI data were fitted to renewal-process models that accounted for the neuron refractory periods and hair-cell synaptic release. Modeling the timing of synaptic release using a mixture of two exponential distributions yielded the best fit for our ISI data. Additionally, lateral line ISIs displayed positive serial correlation and appeared to exhibit switching between faster and slower modes of spike generation. This pattern contrasts with previous findings from the auditory system where ISIs tended to have negative serial correlation due to synaptic depletion. We propose that afferent neuron innervation with multiple and heterogenous hair-cells synapses, each influenced by changes in calcium domains, can serve as a mechanism for the random switching behavior. Overall, our analyses provide evidence of how physiological similarities and differences between synapses and innervation patterns in the auditory, vestibular, and lateral line systems can lead to variations in spontaneous activity.
在没有刺激的情况下，毛细胞会自发释放神经递质，导致支配传入神经元的动作电位（尖峰）自发产生。我们分析了从斑马鱼侧线记录的自发尖峰模式，发现尖峰间隔（ISI）的分布要么呈指数形状，要么呈“L”形状，其特征是急剧衰减但长尾。ISI 数据拟合到了再生过程模型，该模型考虑了神经元不应期和毛细胞突触释放。使用两个指数分布的混合物来模拟突触释放的时间，可以为我们的 ISI 数据提供最佳拟合。此外，侧线 ISI 显示出正的序列相关，并且似乎表现出在更快和更慢的尖峰生成模式之间的切换。这种模式与听觉系统中的先前发现形成对比，在听觉系统中，由于突触耗竭，ISI 往往具有负的序列相关。我们提出，具有多个和异质毛细胞突触的传入神经元支配，每个突触都受到钙域变化的影响，可作为随机切换行为的一种机制。总的来说，我们的分析提供了证据，表明听觉、前庭和侧线系统中的突触和支配模式的生理相似性和差异如何导致自发活动的变化。
