Antal Miklós, Eyre Mark, Finklea Bryson, Nusser Zoltan
Laboratory of Cellular Neurophysiology, Institute of Experimental Medicine, Hungarian Academy of Sciences, Szigony Street 43, 1083 Budapest, Hungary.
Eur J Neurosci. 2006 Aug;24(4):1124-36. doi: 10.1111/j.1460-9568.2006.04988.x.
The glomeruli of the main olfactory bulb are the first processing station of the olfactory pathway, where complex interactions occur between sensory axons, mitral cells and a variety of juxtaglomerular neurons, including external tufted cells (ETCs). Despite a number of studies characterizing ETCs, little is known about how their morphological and functional properties correspond to each other. Here we determined the active and passive electrical properties of ETCs using in vitro whole-cell recordings, and correlated them with their dendritic arborization patterns. Principal component followed by cluster analysis revealed two distinct subpopulations of ETCs based on their electrophysiological properties. Eight out of 12 measured physiological parameters exhibited significant difference between the two subpopulations, including the membrane time constant, amplitude of spike afterhyperpolarization, variance in the interspike interval distribution and subthreshold resonance. Cluster analysis of the morphological properties of the cells also revealed two subpopulations, the most prominent dissimilarity between the groups being the presence or absence of secondary, basal dendrites. Finally, clustering the cells taking all measured properties into account also indicated the presence of two subpopulations that mapped in an almost perfect one-to-one fashion to both the physiologically and the morphologically derived groups. Our results demonstrate that a number of functional and structural properties of ETCs are highly predictive of one another. However, cells within each subpopulation exhibit pronounced variability, suggesting a large degree of specialization evolved to fulfil specific functional requirements in olfactory information processing.
主嗅球的肾小球是嗅觉通路的第一个处理站，感觉轴突、二尖瓣细胞和各种近肾小球神经元（包括外侧簇状细胞，即ETCs）之间在此发生复杂的相互作用。尽管有许多研究对ETCs进行了表征，但对于它们的形态和功能特性如何相互对应却知之甚少。在这里，我们使用体外全细胞膜片钳记录来确定ETCs的主动和被动电学特性，并将它们与其树突分支模式相关联。主成分分析随后进行聚类分析，根据其电生理特性揭示了ETCs的两个不同亚群。在12个测量的生理参数中，有8个在两个亚群之间表现出显著差异，包括膜时间常数、动作电位后超极化幅度、动作电位间隔分布的方差和阈下共振。对细胞形态特性的聚类分析也揭示了两个亚群，两组之间最显著的差异在于是否存在二级基底树突。最后，综合考虑所有测量特性对细胞进行聚类，也表明存在两个亚群，它们几乎以完美的一对一方式映射到生理和形态学衍生的组中。我们的结果表明，ETCs的许多功能和结构特性相互之间具有高度的预测性。然而，每个亚群内的细胞表现出明显的变异性，这表明在嗅觉信息处理中为满足特定功能需求而进化出了很大程度的特化。
