MRC Institute of Hearing Research, Medical Research Council Nottingham, UK.
Front Neural Circuits. 2012 Aug 20;6:55. doi: 10.3389/fncir.2012.00055. eCollection 2012.
The central nucleus of the inferior colliculus (IC) is organized into a series of fibro-dendritic laminae, orthogonal to the tonotopic progression. Many neurons have their dendrites confined to one lamina while others have dendrites that cross over a number of laminae. Here, we have used juxtacellular labeling in urethane anesthetized guinea pigs to visualize the cells with biocytin and have analyzed their response properties, in order to try and link their structure and function. Out of a sample of 38 filled cells, 15 had dendrites confined within the fibro-dendritic laminae and in 13 we were also able to reconstruct their local axonal tree. Based on dendritic morphology they were subdivided into flat or less flat; small, medium, or large; elongated or disk-shaped cells. Two of the elongated cells had many dendritic spines while the other cells had few or none. Twelve of the cells had their local axonal tree restricted to the same lamina as their dendrites while one cell had its dendrites in a separate lamina from the axon. The axonal plexus was more extensive (width 0.7-1.4 mm) within the lamina than the dendrites (width generally 0.07-0.53 mm). The intrinsic axons were largely confined to a single lamina within the central nucleus, but at least half the cells also had output axons with two heading for the commissure and five heading into the brachium. We were able to identify similarities in the physiological response profiles of small groups of our filled cells but none appeared to represent a homogeneous morphological cell type. The only common feature of our sample was one of exclusion in that the onset response, a response commonly recorded from IC cells, was never seen in laminar cells, but was in cells with a stellate morphology. Thus cells with laminar dendrites have a wide variety of physiological responses and morphological subtypes, but over 90% have an extensive local axonal tree within their local lamina.
下丘脑中核（IC）的中央核组织成一系列与音调递增方向正交的纤维-树突层。许多神经元的树突局限于一个层，而其他神经元的树突则跨越多个层。在这里，我们使用在氨基甲酸乙酯麻醉的豚鼠中进行的细胞外标记来可视化具有生物素的细胞，并分析它们的反应特性，以尝试将它们的结构和功能联系起来。在 38 个填充细胞的样本中，有 15 个细胞的树突局限于纤维-树突层内，我们还能够重建它们的局部轴突树。根据树突形态，它们被分为扁平或不太扁平的细胞；小、中、大的细胞；细长或盘状细胞。两个细长的细胞有许多树突棘，而其他细胞有很少或没有树突棘。12 个细胞的局部轴突树局限于与其树突相同的层，而一个细胞的树突与轴突位于不同的层。与树突相比，轴突丛在层内的范围更广（宽度 0.7-1.4 毫米）。内在轴突主要局限于中央核内的单个层内，但至少有一半的细胞也有输出轴突，其中两个朝向连合，五个朝向臂。我们能够识别我们填充细胞的小群组的生理反应谱的相似性，但没有一个似乎代表一个同质的形态细胞类型。我们的样本唯一的共同特征是排斥性，即起始反应，这是从 IC 细胞中经常记录到的反应，在层状细胞中从未见到过，但在具有星状形态的细胞中可见。因此，具有层状树突的细胞具有广泛的生理反应和形态亚型，但超过 90%的细胞在其局部层内具有广泛的局部轴突树。
