Lewis D A, Lund J S
Department of Psychiatry, University of Pittsburgh, Pennsylvania 15213.
J Comp Neurol. 1990 Mar 22;293(4):599-615. doi: 10.1002/cne.902930406.
Chandelier neurons are a unique subclass of cortical nonpyramidal neurons. The axons of these neurons terminate in distinctive vertically arrayed cartridges that synapse on the axon initial segment of pyramidal neurons. In this study, the rapid Golgi method and immunohistochemical techniques were used to characterize the morphology, regional distribution, laminar location, and biochemical content of chandelier neurons in the prefrontal and occipital cortices of three monkey species. As in our previous studies of visual areas V1 and V2 (Lund: Journal of Comparative Neurology 257:60-92, 1987; Lund et al.: Journal of Comparative Neurology 202:19-45, 1981, 276:1-29, 1988), Golgi impregnations of areas 46 and 9 of macaque prefrontal cortex show chandelier neurons to be present in layers 2 through superficial 5. The vertical arrays of terminal boutons (axon cartridges) typical of this neuron class are also present in layers 2-6 of the prefrontal cortex, but are not found in layer 1 or the subcortical white matter. In immunohistochemical studies, a calcium-binding protein, parvalbumin, and a neuropeptide, corticotropin-releasing factor (CRF), identify rod-like structures that are morphologically similar to the axon cartridges of chandelier neurons seen in the Golgi material. In addition, both parvalbumin- and CRF-immunoreactive cartridges are located below the somata of unlabeled pyramidal neurons and appear to outline the axon initial segment of these neurons. However, we find that parvalbumin and CRF are present in only subpopulations of chandelier axon cartridges. For example, in adult primary visual cortex, parvalbumin-labeled cartridges are present in very low numbers only in layers 2-3, whereas in prefrontal and occipital association cortices these cartridges are a very prominent component of layers 2-superficial 3 and are present in much lower density in the deeper cortical layers. In contrast to these findings in adult macaque monkeys, prefrontal and occipital association cortices of infant macaque monkeys contain a very high density of parvalbumin-labeled cartridges in layer 4 and relatively few in the superficial cortical layers. Furthermore, in adult squirrel monkey prefrontal cortex, CRF-labeled cartridges are predominately present in layer 4, but these CRF-immunoreactive structures have not been observed in the homologous regions of infant or adult macaque monkeys. These findings indicate that even for neurons of such distinctive morphology and presumably constant functional role as chandelier neurons, factors such as regional and laminar location, age, and primate species are associated with differences in the biochemical content of subpopulations of these neurons.
吊灯神经元是皮质非锥体神经元的一个独特亚类。这些神经元的轴突终止于独特的垂直排列的小体，这些小体与锥体神经元的轴突起始段形成突触。在本研究中，使用快速高尔基法和免疫组织化学技术来表征三种猴类前额叶和枕叶皮质中吊灯神经元的形态、区域分布、层位定位和生化成分。正如我们之前对视区V1和V2的研究（伦德：《比较神经学杂志》257:60 - 92，1987；伦德等人：《比较神经学杂志》202:19 - 45，1981，276:1 - 29，1988）一样，猕猴前额叶皮质46区和9区的高尔基浸染显示，吊灯神经元存在于2层至浅层5层。这类神经元典型的终末钮（轴突小体）的垂直排列也存在于前额叶皮质的2 - 6层，但在1层或皮质下白质中未发现。在免疫组织化学研究中，一种钙结合蛋白——小白蛋白，以及一种神经肽——促肾上腺皮质激素释放因子（CRF），可识别出形态上类似于在高尔基材料中看到的吊灯神经元轴突小体的杆状结构。此外，小白蛋白和CRF免疫反应性小体都位于未标记锥体神经元的胞体下方，并且似乎勾勒出这些神经元的轴突起始段。然而，我们发现小白蛋白和CRF仅存在于吊灯轴突小体的亚群中。例如，在成年初级视皮质中，仅在2 - 3层中存在数量非常少的小白蛋白标记的小体，而在前额叶和枕叶联合皮质中，这些小体是2层至浅层3层的一个非常突出的成分，并且在皮质深层中的密度要低得多。与成年猕猴的这些发现相反，幼年猕猴的前额叶和枕叶联合皮质在4层中含有非常高密度的小白蛋白标记的小体，而在皮质浅层中相对较少。此外，在成年松鼠猴的前额叶皮质中，CRF标记的小体主要存在于4层，但在幼年或成年猕猴的同源区域中未观察到这些CRF免疫反应性结构。这些发现表明，即使对于像吊灯神经元这样形态独特且功能作用可能恒定的神经元，区域和层位定位、年龄以及灵长类物种等因素也与这些神经元亚群的生化成分差异相关。
