Naumann T, Linke R, Frotscher M
Institute of Anatomy, University of Freiburg, Germany.
J Comp Neurol. 1992 Nov 8;325(2):207-18. doi: 10.1002/cne.903250206.
In this report the normal dendritic organization and fine structure of identified septohippocampal projection neurons is described as a prerequisite for a time course analysis of retrograde changes in these neurons following axotomy (see Naumann et al., J. Comp. Neurol. 325:219-242, 1992). Septohippocampal projection neurons were retrogradely labeled by injection of the fluorescent tracer Fluoro-Gold into the hippocampus. Next, retrogradely labeled cells in Vibratome sections of the medial septum/diagonal band complex were intracellularly stained with the fluorescent dye Lucifer Yellow (LY). Photooxidation of LY resulted in a stable electron-dense reaction product, which allowed us to study these double-labeled neurons by electron microscopy. Another series of sections containing retrogradely labeled neurons were immunostained for choline acetyltransferase (ChAT) or parvalbumin (PARV). In this way the fine structure of two different chemically characterized subpopulations of septohippocampal neurons could be compared with that of the LY-injected neurons. Intracellular filling of retrogradely labeled neurons with LY stained the cell body and the entire dendritic arbor. Essentially, three classes of neurons could be distinguished, i.e., bipolar cells, multipolar neurons, and an intermediate group. All these neurons displayed smooth, often varicose dendrites lacking spines. Mainly located close to the midline, there was a group of cells with only very few if any LY-stained dendrites. In the electron microscope, the double-labeled neurons were easily identified by numerous electron-dense lysosomes associated with transported Fluoro-Gold and the diffuse reaction product resulting from photooxidation. They displayed fine-structural characteristics as previously described for cholinergic neurons. In fact, our fine-structural analysis of ChAT-positive Fluoro-Gold-labeled neurons, but also of back-filled PARV-positive cells, gave very similar results. All these neurons had infolded nuclei, abundant cytoplasmic organelles, and a few axosomatic synapses. Thus, a plain electron microscopic study does not allow one to distinguish between subpopulations of septohippocampal projection neurons.
在本报告中，已鉴定的隔海马投射神经元的正常树突组织和精细结构被描述为对这些神经元在轴突切断后逆行变化进行时程分析的前提条件（见瑙曼等人，《比较神经学杂志》325:219 - 242，1992）。通过将荧光示踪剂氟金注射到海马体中，对隔海马投射神经元进行逆行标记。接下来，在内侧隔核/斜角带复合体的振动切片中，用荧光染料路西法黄（LY）对逆行标记的细胞进行细胞内染色。LY的光氧化产生了一种稳定的电子致密反应产物，这使我们能够通过电子显微镜研究这些双重标记的神经元。另一系列包含逆行标记神经元的切片用胆碱乙酰转移酶（ChAT）或小白蛋白（PARV）进行免疫染色。通过这种方式，可以将隔海马神经元的两个不同化学特征亚群的精细结构与注射了LY的神经元的精细结构进行比较。用LY对逆行标记的神经元进行细胞内填充，可对细胞体和整个树突分支进行染色。基本上，可以区分出三类神经元，即双极细胞、多极神经元和中间组。所有这些神经元都显示出光滑的、通常有曲张的无棘树突。主要位于中线附近，有一组细胞，其LY染色的树突极少甚至没有。在电子显微镜下，通过与运输的氟金相关的大量电子致密溶酶体以及光氧化产生的弥散反应产物，可以很容易地识别出双重标记的神经元。它们表现出如先前所述的胆碱能神经元的精细结构特征。事实上，我们对ChAT阳性的氟金标记神经元以及回充的PARV阳性细胞的精细结构分析得出了非常相似的结果。所有这些神经元都有内陷的细胞核、丰富的细胞质细胞器以及一些轴体突触。因此，单纯的电子显微镜研究无法区分隔海马投射神经元的亚群。
