Kawaja M D, Gage F H
Department of Neurosciences, University of California, San Diego, La Jolla 92093-0624.
J Comp Neurol. 1991 May 15;307(3):517-29. doi: 10.1002/cne.903070313.
Nerve growth factor receptor immunoreactivity in the septohippocampal pathway of adult Fischer 344 rats was assessed at the light and electron microscope level. The medial septum possesses immunoreactive somata, dendrites, axons, and terminals. Immunostained somata are either bipolar or multipolar in appearance. Dendritic processes of immunoreactive septal neurons are categorized into two groups: proximal dendrites with smooth plasma membranes and distal dendrites with numerous swellings. Immunoreactive axons within the septum are long and slender and do not possess varicosities. At the electron microscope level, immunoreactivity is confined predominantly to the plasma membrane of cell bodies and dendrites of septal neurons, as well as to the plasma membrane of axons and terminals. Both immunoreactive and nonimmunoreactive terminals that contain clear, spherical vesicles are observed contacting immunoreactive dendrites and somata. Although accumulations of vesicles are evident within these terminals at sites of contact, distinct synaptic specializations are difficult to distinguish due to the localization of reaction product on the apposing plasma membranes. Axons possessing immunoreactivity are also observed in the fimbria-fornix pathway, a major source of afferent inputs to the hippocampus. Immunoreactive axons and terminals are topographically organized in the hippocampal dentate gyrus. The density of immunostained axons and terminals is highest immediately adjacent to the granular layer. In comparison, a moderate density of immunoreactive axons is found in the outer molecular layer and a weak density in the inner molecular, granular, and polymorphic layers. Immunoreactivity is found on the plasma membrane of small unmyelinated axons and terminals aggregated into clusters throughout the dentate gyrus. Definitive examples of axosomatic and axodendritic synapses possessing immunoreactivity presynaptically are not observed. Immunoreactive profiles within the medial septum and hippocampus also circumfuse a small number of intracerebral vessels. Ultrastructural examination reveals that immunoreactivity is present within a narrowed extension of the subarachnoid space and appears to be closely associated with the plasma membrane of leptomeningeal cell processes. The present study provides direct evidence for the cellular distribution of nerve growth factor receptor immunoreactivity in the medial septum and dentate gyrus in the adult rat and offers new insight into the ultrastructural localization of nerve growth factor receptor among septal cholinergic neurons and their efferent projections to the hippocampus.
在光镜和电镜水平上评估成年Fischer 344大鼠隔海马通路中的神经生长因子受体免疫反应性。内侧隔区有免疫反应性的胞体、树突、轴突和终末。免疫染色的胞体外观呈双极或多极。免疫反应性隔区神经元的树突过程分为两组：具有光滑质膜的近端树突和具有许多肿胀的远端树突。隔区内的免疫反应性轴突长而细，没有膨体。在电镜水平上，免疫反应性主要局限于隔区神经元胞体和树突的质膜，以及轴突和终末的质膜。观察到含有清亮球形囊泡的免疫反应性和非免疫反应性终末与免疫反应性树突和胞体接触。尽管在这些终末的接触部位囊泡聚集明显，但由于反应产物定位于相对的质膜上，难以区分明显的突触特化结构。在海马的主要传入纤维来源——穹窿-海马伞通路中也观察到具有免疫反应性的轴突。免疫反应性轴突和终末在海马齿状回中呈拓扑学排列。免疫染色的轴突和终末密度在紧邻颗粒层处最高。相比之下，在外分子层发现中等密度的免疫反应性轴突，在内分子层、颗粒层和多形层中密度较弱。在整个齿状回中，小的无髓鞘轴突和终末聚集形成簇，其质膜上有免疫反应性。未观察到突触前具有免疫反应性的确切轴-体和轴-树突触实例。内侧隔区和海马内的免疫反应性轮廓也围绕着少数脑内血管。超微结构检查显示，免疫反应性存在于蛛网膜下腔的一个狭窄延伸部位，似乎与软脑膜细胞突起的质膜密切相关。本研究为成年大鼠内侧隔区和齿状回中神经生长因子受体免疫反应性的细胞分布提供了直接证据，并为神经生长因子受体在隔区胆碱能神经元及其向海马的传出投射中的超微结构定位提供了新的见解。
