Zhang C, Wong-Riley M T
Department of Cellular Biology and Anatomy, Medical College of Wisconsin, Milwaukee 53226, USA.
Brain Res. 1996 Aug 12;729(2):205-15.
The activation of nitric oxide synthase (NOS) has been linked to excitatory input via NMDA receptors. We hypothesized that NOS-positive neurons that have NMDA receptors on their surface would have high levels of cytochrome oxidase (C.O.) as energy generator for membrane repolarization. In order to compare the distribution of these markers on the same section, we reacted rat brain sections for C.O. histochemistry followed by NOS immunogold silver staining (IGSS). Adjacent sections were reacted for NOS IGSS followed by indirect immunoperoxidase for NMDA receptor subunit R1 (NMDAR1). We found that the staining pattern varied among regions but were consistent within each region examined. There are three types of NOS immunoreactive (NOS-ir) cells: (1) NOS-ir neurons that had moderate to high levels of both NMDAR1 and C.O. staining, such as the pontine reticular nuclei, motor and mesencephalic nuclei of the trigeminal nerve, and some motor neurons in the spinal cord. (2) NOS-ir neurons that were immunoreactive for NMDAR1 (NMDAR1-ir) but had low levels of C.O. activity in thei- somata. Their dendrites, however, were both NMDAR1-ir and rich in C.O. Examples of this type include neurons in the caudate and putamen, and periglomerular cells in the olfactory bulb. (3) We also found that some NOS-ir neurons were not NMDAR1-ir and had low C.O. activity. In addition to postsynaptic neurons, C.O. and NOS levels were both high in the inner segments of retinal photoreceptor cells where energy-demanding active ion transport maintains the dark current and where NO presumably activates guanylate cyclase for the production of cGMP, which keeps the Na+ channels open in the dark. Our findings suggest that NMDA receptors are available for the majority of NOS-ir neurons, which comprise a heterogenous population with varying energy demands.
一氧化氮合酶（NOS）的激活已被证明与通过NMDA受体的兴奋性输入有关。我们推测，其表面具有NMDA受体的NOS阳性神经元会有高水平的细胞色素氧化酶（C.O.），作为膜复极化的能量来源。为了在同一切片上比较这些标志物的分布，我们先对大鼠脑切片进行C.O.组织化学反应，然后进行NOS免疫金银染色（IGSS）。相邻切片先进行NOS IGSS反应，然后用间接免疫过氧化物酶法检测NMDA受体亚基R1（NMDAR1）。我们发现，染色模式在不同区域有所不同，但在每个检查区域内是一致的。有三种类型的NOS免疫反应性（NOS-ir）细胞：（1）NOS-ir神经元，其NMDAR1和C.O.染色水平中等至较高，如脑桥网状核、三叉神经运动核和中脑核，以及脊髓中的一些运动神经元。（2）对NMDAR1有免疫反应（NMDAR1-ir）但胞体中C.O.活性较低的NOS-ir神经元。然而，它们的树突既是NMDAR1-ir且富含C.O.。这种类型的例子包括尾状核和壳核中的神经元，以及嗅球中的球周细胞。（3）我们还发现一些NOS-ir神经元不是NMDAR1-ir且C.O.活性较低。除了突触后神经元外，视网膜光感受器细胞内段的C.O.和NOS水平都很高，在那里需要能量的主动离子转运维持暗电流，并且NO可能激活鸟苷酸环化酶以产生cGMP，从而使Na+通道在黑暗中保持开放。我们的研究结果表明，大多数NOS-ir神经元都有NMDA受体，这些神经元构成了一个具有不同能量需求的异质群体。
