Wang H, Morris J F
Department of Human Anatomy, University of Oxford, U.K.
Neuroscience. 1996 Oct;74(4):1059-68. doi: 10.1016/0306-4522(96)00165-0.
Nitric oxide has recently been identified as a major neural regulator. It is synthesized by the enzyme nitric oxide synthase. Whilst considerable functional evidence has pointed to an involvement of nitric oxide in circadian regulation, all previous morphological studies have failed to demonstrate the presence of nitric oxide synthase in the mammalian suprachiasmatic nucleus. By use of an antibody directed against whole recombinant rat neuronal nitric oxide synthase we have identified the presence of immunoreactivity for this enzyme in the suprachiasmatic nucleus of mouse and rat, to provide the first detailed report of this enzyme in the suprachiasmatic nucleus for any species of mammal. Immunoreactivity for neuronal nitric oxide synthase was found in neurons throughout the suprachiasmatic nucleus of mice and no difference could be detected between the ventrolateral and dorsomedial parts of the nucleus in terms of the optical density of the immunostaining. Very small, rounded neuronal cell bodies were immunopositive. Electron microscopy revealed that these neurons had relatively large nuclei and scant cytoplasm containing relatively few organelles, which sometimes included some 100 nm dense-cored peptidergic vesicles. Only about 5% of such neurons were not detectably immunoreactive. By contrast, in the rat suprachiasmatic nucleus, a much smaller number of neurons were immunopositive and these cells were aggregated in the ventrolateral part of the nucleus. The immunoreactive neurons were bipolar cells with scanty cytoplasm. Electron microscopy revealed diffuse immunoreactivity in the cytosol, but not within any organelles. In the surrounding neuropil immunoreactive dendrites and axons mingled with much larger numbers of immunonegative processes, but immunoreactive boutons were only identified just outside the dorsal margin of the nucleus. Astrocytes, oligodendrocytes and endothelial cells in the suprachiasmatic nucleus were immunonegative. NADPH-diaphorase activity was not detectable in the suprachiasmatic nucleus of either mouse or rat. This morphological evidence for nitric oxide synthase-immunoreactive cells in the suprachiasmatic nucleus supports the existing functional evidence for an involvement of nitric oxide in the transmission of light-induced signals to the suprachiasmatic nucleus in mammals.
一氧化氮最近被确认为一种主要的神经调节因子。它由一氧化氮合酶合成。尽管大量功能证据表明一氧化氮参与昼夜节律调节，但以往所有形态学研究均未能证明哺乳动物视交叉上核中存在一氧化氮合酶。通过使用针对整个重组大鼠神经元一氧化氮合酶的抗体，我们在小鼠和大鼠的视交叉上核中鉴定出了该酶的免疫反应性，这是首次针对任何哺乳动物物种视交叉上核中该酶的详细报告。在小鼠视交叉上核的所有神经元中均发现了神经元一氧化氮合酶的免疫反应性，并且在该核的腹外侧和背内侧部分之间，就免疫染色的光密度而言，未检测到差异。非常小的圆形神经元细胞体呈免疫阳性。电子显微镜显示，这些神经元具有相对较大的细胞核和含有相对较少细胞器的少量细胞质，这些细胞器有时包括一些100纳米的致密核心肽能小泡。只有约5%的此类神经元未检测到免疫反应性。相比之下，在大鼠视交叉上核中，免疫阳性的神经元数量要少得多，这些细胞聚集在该核的腹外侧部分。免疫反应性神经元是细胞质稀少的双极细胞。电子显微镜显示，细胞质中存在弥漫性免疫反应性，但细胞器内未检测到。在周围神经纤维中，免疫反应性树突和轴突与大量免疫阴性的突起混合在一起，但仅在该核背缘外侧才鉴定出免疫反应性终扣。视交叉上核中的星形胶质细胞、少突胶质细胞和内皮细胞呈免疫阴性。在小鼠或大鼠的视交叉上核中均未检测到NADPH - 黄递酶活性。视交叉上核中一氧化氮合酶免疫反应性细胞的这一形态学证据支持了一氧化氮参与将光诱导信号传递至哺乳动物视交叉上核的现有功能证据。
