Auditory Neurophysiology Unit, Institute of Neuroscience of Castilla y León, University of Salamanca, 37007 Salamanca, Spain.
Hear Res. 2011 Apr;274(1-2):13-26. doi: 10.1016/j.heares.2010.06.011. Epub 2010 Jun 22.
The inferior colliculus (IC) is the main auditory nucleus in the midbrain. This auditory center is made of a central nucleus (CNIC) characterized by a distinct laminar organization that is surrounded by cortical regions. The neuronal types in the CNIC are well established but thus far, the neuronal composition and functional roles of the cortical regions are not fully appreciated. As dendritic architecture is critical for the synaptic integrative properties of neurons, a detailed analysis of the dendritic architecture of the neurons in the collicular cortical regions should shed light on our understanding of their roles in collicular function. In the present study, we have used the del Rio-Hortega Golgi procedure to impregnate individual neurons within the IC. Rat brains were embedded in resin and sectioned serially to allow quantitative 3-D analyses of single neurons or groups of neurons. Our results demonstrate that the cortical regions of the IC are made up of unique sets of neuronal types and that there is an interdigitation of dendrites at the cortical borders. This latter feature may have led to difficulty in delineating a sharp border between the CNIC and cortical regions in previous studies. The quantitative analysis further demonstrates that there are significant differences in many of the dendritic parameters tested when compared to the neurons from the CNIC. Moreover, we observed that the neuronal populations of the cortical regions vary from the laminar pattern of the CNIC and from each other. Since the main organizing principle of the CNIC is the laminar organization of 'flat' neurons, evidence that cortical IC regions lack flat neurons supports the subdivision schema presented here.
下丘（IC）是中脑的主要听觉核。这个听觉中枢由一个中央核（CNIC）组成，其特征是具有明显的层状组织，被皮质区域包围。CNIC 中的神经元类型已经确定，但迄今为止，皮质区域的神经元组成和功能作用还没有得到充分的认识。由于树突结构对于神经元的突触整合特性至关重要，因此对丘状皮质区域神经元的树突结构进行详细分析，应该有助于我们理解它们在丘状功能中的作用。在本研究中，我们使用了 del Rio-Hortega Golgi 程序来对 IC 中的单个神经元进行染色。大鼠脑被嵌入树脂中并进行连续切片，以便对单个神经元或神经元群进行定量 3D 分析。我们的结果表明，IC 的皮质区域由独特的神经元类型组成，并且在皮质边界处存在树突的交错。这一特征可能导致以前的研究中很难在 CNIC 和皮质区域之间划出清晰的边界。定量分析进一步表明，与 CNIC 中的神经元相比，许多树突参数存在显著差异。此外，我们观察到皮质区域的神经元群体与 CNIC 的层状模式和彼此之间存在差异。由于 CNIC 的主要组织原则是“扁平”神经元的层状组织，因此皮质 IC 区域缺乏扁平神经元的证据支持了这里提出的细分方案。
