Yamamoto T, Maler L, Hertzberg E L, Nagy J I
Department of Physiology, Faculty of Medicine, University of Manitoba, Winnipeg, Canada.
J Comp Neurol. 1989 Nov 15;289(3):509-36. doi: 10.1002/cne.902890314.
Electrotonic transmission via gap junctions appears to be essential for both the relay and integration of information in nuclear groups involved in the electrolocation and electrocommunication systems of weakly electric fish. An affinity-purified antibody against the 27 kD gap-junctional polypeptide (GJP) from rat liver was used to determine immunohistochemically the distribution of GJP-immunoreactivity (GJP-IR) in electrosensory structures and some other brain regions of the gymnotiform fish, Apteronotus leptorhynchus. At the ultrastructural level, immunolabelling with this antibody was localized, in part, to neuronal and glial gap junctions where it was assumed to recognize a junctional polypeptide. By light microscopy, the vast majority of immunoreactive elements appeared either as fine puncta or as varicosities along fibers that exhibited immunostained intervaricose segments. Diffuse immunoreactivity within cell bodies was rare, being most evident in giant relay neurons and presumptive glial cells within the pacemaker nucleus and in neurons within the posterior raphe nucleus. The distribution of punctate and fibrous GJP-IR was remarkably heterogeneous with respect to density; large areas of the forebrain and most major fiber tracts were nearly devoid of immunoreactivity, whereas concentrations of puncta delineating patches within the inferior lobe of the hypothalamus and the vagal sensory nucleus were so dense as to appear as uniform deposition of immunoperoxidase reaction product at low magnification. Some structures known to be associated with the electrosensory system, including the nucleus electrosensorius and nucleus praeeminentialis, were among the brain regions containing the highest concentrations of immunoreactivity. At the cellular level, expected patterns of GJP-IR were observed in the pacemaker nucleus, torus semicircularis, and electrosensory lateral line lobe. In each of these structures punctate immunoreactivity was seen in apposition to cell bodies or dendrites of neurons known to receive gap junction contacts. In addition, the dendrites of neurons within the prepacemaker nucleus were laden with a striking array of puncta, suggesting that interactions via gap junctions may be a significant feature of these neurons. These immunohistochemical results are consistent with previous electrophysiological and ultrastructural observations pointing to the importance of electrotonic communication in the electrosensory system of weakly electric fish, and suggest that gap junctions may also contribute to neural transmission in central nervous system related to other functions in these teleosts.(ABSTRACT TRUNCATED AT 400 WORDS)
通过缝隙连接进行的电紧张性传递似乎对于弱电鱼电定位和电通讯系统中相关核团的信息传递和整合至关重要。使用一种针对大鼠肝脏27 kD缝隙连接多肽（GJP）的亲和纯化抗体，通过免疫组织化学方法来确定GJP免疫反应性（GJP-IR）在裸背电鳗（Apteronotus leptorhynchus）的电感觉结构和一些其他脑区中的分布。在超微结构水平上，用该抗体进行的免疫标记部分定位于神经元和胶质细胞的缝隙连接，推测其能识别一种连接多肽。通过光学显微镜观察，绝大多数免疫反应元件表现为细点状或沿纤维的曲张体，这些纤维的曲张体间节段呈现免疫染色。细胞体内的弥漫性免疫反应很少见，在起搏器核内的巨型中继神经元和假定的胶质细胞以及后中缝核内的神经元中最为明显。点状和纤维状GJP-IR的分布在密度方面显著不均一；前脑的大片区域和大多数主要纤维束几乎没有免疫反应性，而下丘脑下叶和迷走感觉核内勾勒出斑块的点状聚集非常密集，以至于在低倍放大时看起来像是免疫过氧化物酶反应产物的均匀沉积。一些已知与电感觉系统相关的结构，包括电感觉核和前主核，是免疫反应性浓度最高的脑区之一。在细胞水平上，在起搏器核、半规管隆起和电感觉侧线叶中观察到了预期的GJP-IR模式。在这些结构中的每一个中，在已知接受缝隙连接接触的神经元的细胞体或树突旁可见点状免疫反应性。此外，前起搏器核内神经元的树突上布满了大量明显的点状结构，这表明通过缝隙连接的相互作用可能是这些神经元的一个重要特征。这些免疫组织化学结果与先前的电生理和超微结构观察结果一致，表明电紧张性通讯在弱电鱼电感觉系统中的重要性，并提示缝隙连接也可能有助于这些硬骨鱼与其他功能相关的中枢神经系统中的神经传递。（摘要截短于400字）
