Moro V, Badaut J, Springhetti V, Edvinsson L, Seylaz J, Lasbennes F
Laboratoire de Recherches Cérébrovasculaires, CNRS URA 641, IFR Circulation Lariboisière, Université Paris VII, France.
Neuroscience. 1995 Dec;69(3):797-805. doi: 10.1016/0306-4522(95)00285-q.
There is increasing evidence that nitric oxide is an important molecular messenger involved in a wide variety of biological processes including the regulation of the cerebral circulation. For instance, it has been implicated in the vascular response to nucleus basalis magnocellularis stimulation, a structure which is widely recognized as the predominant source of cholinergic fibres projecting to the neocortex. The present investigation was carried out to determine if muscarinic receptors are present on cortical neurons expressing neuronal nitric oxide synthase (nitric oxide-producing enzyme). To this aim, double labelling of both neuronal nitric oxide synthase/vessels and neuronal nitric oxide synthase/muscarinic receptors was performed on free-floating cryosections obtained from rat brain. The observations were made by confocal laser scanning microscopy. The double labelling of neuronal nitric oxide synthase with the arterioles demonstrated the presence of nitroxidergic fibres in the wall of intraparenchymal vessels. A rich network of nitroxidergic fibres independent of the vessels was also seen in the parenchyma. Since the maximal surface of a square of tissue without any nitroxidergic fibres corresponded to 1400 +/- 105 microns2, the distance separating any cortical point from its closest neuronal nitric oxide synthase-positive fibre was never higher than 25 microns (half diagonal of square). According to models of the diffusional spread of nitric oxide, it is likely that nitric oxide can reach the whole cortical volume. Our results on the regional study of neuronal nitric oxide synthase/muscarinic receptors showed a high density of neuronal nitric oxide synthase-positive neurons principally in the frontal and perirhinal cortices and a low density in the occipital cortex. These data fit well with the known pattern of cortical projections from the nucleus basalis magnocellularis as revealed by anterogradely transported markers. The double labelling showed that about 10% of neuronal nitric oxide synthase-positive neurons were co-localized with muscarinic receptors in the frontoparietal cortex. In agreement with previous papers, the vascular innervation by nitroxidergic neuronal processes was often found to lie near the branching points of arterioles. Such localization allows neuronal nitric oxide synthase-positive neurons an extensive control of the vascular tree without requiring a large number of neuronal commands. Therefore, despite the low level of neuronal nitric oxide synthase/muscarinic receptor co-localization, this neuronal subpopulation could represent a possible relay implicated in the vascular effects of the nucleus basalis magnocellularis.
越来越多的证据表明，一氧化氮是一种重要的分子信使，参与包括脑循环调节在内的多种生物过程。例如，它与基底核大细胞刺激引起的血管反应有关，基底核大细胞是广泛公认的投射到新皮层的胆碱能纤维的主要来源。本研究旨在确定表达神经元型一氧化氮合酶（产生一氧化氮的酶）的皮质神经元上是否存在毒蕈碱受体。为此，对取自大鼠脑的游离漂浮冰冻切片进行了神经元型一氧化氮合酶/血管和神经元型一氧化氮合酶/毒蕈碱受体的双重标记。通过共聚焦激光扫描显微镜进行观察。神经元型一氧化氮合酶与小动脉的双重标记显示实质内血管壁中存在含一氧化氮的纤维。在实质中还可见到一个不依赖于血管的丰富的含一氧化氮纤维网络。由于没有任何含一氧化氮纤维的组织方块的最大面积为1400±105平方微米，所以从皮质的任何一点到其最接近的神经元型一氧化氮合酶阳性纤维的距离从不超过25微米（方块的半对角线）。根据一氧化氮扩散传播的模型，一氧化氮很可能能够到达整个皮质区域。我们关于神经元型一氧化氮合酶/毒蕈碱受体区域研究的结果显示，神经元型一氧化氮合酶阳性神经元主要集中在额叶和嗅周皮质，而枕叶皮质中的密度较低。这些数据与通过顺行转运标记物揭示的基底核大细胞的已知皮质投射模式非常吻合。双重标记显示，在额顶叶皮质中，约10%的神经元型一氧化氮合酶阳性神经元与毒蕈碱受体共定位。与先前的论文一致，经常发现含一氧化氮的神经突的血管支配位于小动脉的分支点附近。这种定位使神经元型一氧化氮合酶阳性神经元能够在不需要大量神经指令的情况下对血管树进行广泛控制。因此，尽管神经元型一氧化氮合酶/毒蕈碱受体的共定位水平较低，但这个神经元亚群可能代表了参与基底核大细胞血管效应的一个可能的中继环节。
