Fonseca M, Soriano E, Ferrer I, Martinez A, Tuñon T
Department of Neuroscience, Faculty of Medicine, University of The Basque Country, Leioa, Spain.
Neuroscience. 1993 Aug;55(4):1107-16. doi: 10.1016/0306-4522(93)90324-9.
Parvalbumin is a calcium-binding protein which is thought to play a role in neuronal excitability. In the cerebral cortex parvalbumin is largely found in two subsets of GABAergic neurons, the chandelier and basket cells. A distinguishing characteristic of the chandelier cell is that the terminal portions of its axon form short vertical strings of boutons resembling candlesticks, which embrace the initial segment of pyramidal cell axon. In the present study, the terminals of chandelier cells in the human temporal cortex were immunostained with an antibody against parvalbumin. These terminals were found more abundantly in layers II and VI, less frequently in layers III and V, were hardly identified in layer IV, and absent in layer I. The relationship of parvalbumin-immunoreactive terminals and axon initial segments was further evidenced by re-sectioning identified rows of boutons into semithin sections. Electron microscopy of both temporal cortex and the somatosensory region of a biopsy sample revealed that these parvalbumin-positive boutons indeed form symmetric synaptic contacts on the axon initial segments of pyramidal cells. As part of an enquiry into the possibility that these specialized interneurons may be involved in degenerative neurological diseases, the temporal lobes from seven patients with Alzheimer's disease were immunostained for parvalbumin. As in the control brains, the specific terminal portions of chandelier cells were recognized and identified in the temporal cortex by parvalbumin-immunocytochemistry. No major difference from normal brains was found, excepting for a lower density of candlesticks (30-35%) in layer II-III. Since we showed in a previous study [Ferrer et al. (1991) J. neurol. Sci. 106, 135-141] that the number of parvalbumin-immunoreactive somata in the same Alzheimer's disease cases was not decreased, the observed reduction of terminals in layer II suggest that only the terminals of chandelier cells, but not the parent neurons, are decreased in Alzheimer's disease.
小白蛋白是一种钙结合蛋白，被认为在神经元兴奋性中起作用。在大脑皮层中，小白蛋白主要存在于两类γ-氨基丁酸能神经元中，即吊灯细胞和篮状细胞。吊灯细胞的一个显著特征是其轴突的末端部分形成短的垂直串状终扣，类似于烛台，环绕着锥体细胞轴突的起始段。在本研究中，用人颞叶皮质中吊灯细胞的终末用抗小白蛋白抗体进行免疫染色。这些终末在第II层和第VI层中更为丰富，在第III层和第V层中较少见，在第IV层中几乎无法识别，在第I层中不存在。通过将已识别的终扣排重新切片制成半薄切片，进一步证实了小白蛋白免疫反应性终末与轴突起始段的关系。对颞叶皮质和活检样本体感区的电子显微镜检查显示，这些小白蛋白阳性终扣确实在锥体细胞的轴突起始段上形成了对称的突触联系。作为对这些特殊中间神经元可能参与退行性神经疾病可能性研究的一部分，对7例阿尔茨海默病患者的颞叶进行了小白蛋白免疫染色。与对照脑一样，通过小白蛋白免疫细胞化学在颞叶皮质中识别并鉴定出吊灯细胞的特定终末部分。除了第II-III层中烛台密度较低（30-35%）外，未发现与正常脑有重大差异。由于我们在先前的研究[费雷尔等人（1991年）《神经科学杂志》106，135-141]中表明，在相同的阿尔茨海默病病例中，小白蛋白免疫反应性胞体的数量并未减少，因此在第II层中观察到的终末减少表明，在阿尔茨海默病中，只有吊灯细胞的终末减少，而母神经元未减少。
