Resting Discharge Patterns of Macular Primary Afferents in Otoconia-Deficient Mice
Resting Discharge Patterns of Macular Primary Afferents in Otoconia-Deficient Mice
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DOI：
10.1007/s10162-008-0132-0
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发表时间：
2008-12-01
影响因子：
2.4
通讯作者：
Hoffman, L. F.
中科院分区：
文献类型：
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作者：
Jones, T. A.;Jones, S. M.;Hoffman, L. F.
正常哺乳动物的前庭初级传入神经是自发活动的。共识假说认为，这种放电模式是独立的刺激，而是依赖于前庭毛细胞的兴奋，由于背景释放突触神经递质。在耳锥感觉感受器的情况下，很难测试静息放电与重力引起的自然紧张刺激的独立性。我们研究了这个问题，通过研究单一前庭初级传入神经元的放电模式，在重力刺激的情况下，使用两个突变株的小鼠，缺乏耳石（OTO-;头倾斜，het-Nox 3，倾斜，tlt-Otop 1）。我们的研究结果表明，黄斑初级传入神经元表现出强大的休息放电活动在OTO-小鼠。峰电位间隔变异系数（C=SD/平均峰电位间隔）值反映了OTO-小鼠的规则和不规则放电模式，速率标准化CV的值范围与具有完整耳锥的小鼠和其他哺乳动物相似，尽管不规则纤维比例较少。即使考虑到不规则纤维的比例更少，耳锥缺陷型菌株的平均放电率也略高[OTO-=75.4 +/- 31.1（113）vs OTO+=68.1 +/- 28.5（143），sp/s]。这些结果证实了这一假设，即静息活动在黄斑初级传入发生在没有环境刺激。强大的放电率是有趣的，因为它们可能反映了存在的功能'上调'强直性兴奋过程中的自然感觉刺激的情况下。
Vestibular primary afferents in the normal mammal are spontaneously active. The consensus hypothesis states that such discharge patterns are independent of stimulation and depend instead on excitation by vestibular hair cells due to background release of synaptic neurotransmitter. In the case of otoconial sensory receptors, it is difficult to test the independence of resting discharge from natural tonic stimulation by gravity. We examined this question by studying discharge patterns of single vestibular primary afferent neurons in the absence of gravity stimulation using two mutant strains of mice that lack otoconia (OTO-; head tilt, het-Nox3, and tilted, tlt-Otop1). Our findings demonstrated that macular primary afferent neurons exhibit robust resting discharge activity in OTO- mice. Spike interval coefficient of variation (C=SD/mean spike interval) values reflected both regular and irregular discharge patterns in OTO- mice, and the range of values for rate-normalized CV was similar to mice and other mammals with intact otoconia although there were proportionately fewer irregular fibers. Mean discharge rates were slightly higher in otoconia-deficient strains even after accounting for proportionately fewer irregular fibers [OTO-=75.4 +/- 31.1(113) vs OTO+=68.1 +/- 28.5(143) in sp/s]. These results confirm the hypothesis that resting activity in macular primary afferents occurs in the absence of ambient stimulation. The robust discharge rates are interesting in that they may reflect the presence of a functionally 'up-regulated' tonic excitatory process in the absence of natural sensory stimulation.