Hornung Jean-Pierre
Institut de biologie cellulaire et de morphologie, University of Lausanne, Rue du Bugnon 9, 1005, Lausanne, Switzerland.
J Chem Neuroanat. 2003 Dec;26(4):331-43. doi: 10.1016/j.jchemneu.2003.10.002.
The raphe nuclei are distributed near the midline of the brainstem along its entire rostro-caudal extension. The serotonergic neurons are their main neuronal components, although a proportion of them lie in subdivisions of the lateral reticular formation. They develop from mesopontine and medullary primordia, and the resulting grouping into rostral and caudal clusters is maintained into adulthood, and is reflected in the connectivity. Thus, the mesencephalon and rostral pons, neurons within the rostral raphe complex (caudal linear, dorsal raphe, and median raphe nuclei) project primarily to the forebrain. By contrast, in the caudal pons and medulla oblongata, neurons within the caudal raphe complex (raphe magnus, raphe obscurus, raphe pallidus nuclei and parts of the adjacent lateral reticular formation) project to the brainstem nuclei and to the spinal cord. The median raphe and dorsal raphe nuclei provide parallel and overlapping projections to many forebrain structures with axon fibers exhibiting distinct structural and functional characteristics. The caudal group of the serotonergic system projects to the brainstem, and, by three parallel projections, to the dorsal, intermediate and ventral columns in the spinal cord. The serotonergic axons arborize over large areas comprising functionally diverse targets. Some projections form classical chemical synapses while many do not, thus contributing to the so-called paracrine or volume transmission. The serotonergic projections participate in the regulation of different functional (motor, somatosensory, limbic) systems; and have been associated with a wide range of neuropsychiatric and neurological disorders. Finally, recent experimental data support the role of serotonin in modulating brain development, such that a dysfunction in serotonergic transmission during early life could lead to long lasting structural and functional alterations.
中缝核沿着脑干的整个前后延伸分布在脑干中线附近。血清素能神经元是其主要的神经元组成部分，尽管其中一部分位于外侧网状结构的亚区。它们从中脑桥脑和延髓原基发育而来，由此形成的头侧和尾侧簇状结构在成年期得以保留，并反映在其连接性上。因此，在中脑和脑桥上部，头侧中缝复合体（尾侧线性核、背侧中缝核和中缝正中核）内的神经元主要投射到前脑。相比之下，在脑桥下部和延髓，尾侧中缝复合体（中缝大核、中缝隐核、中缝苍白核以及相邻外侧网状结构的部分区域）内的神经元投射到脑干核团和脊髓。中缝正中核和背侧中缝核向许多前脑结构提供平行且重叠的投射，其轴突纤维表现出独特的结构和功能特征。血清素能系统的尾侧组投射到脑干，并通过三条平行投射通路，投射到脊髓的背侧、中间和腹侧柱。血清素能轴突在包含功能多样靶点的大面积区域形成分支。一些投射形成经典的化学突触，而许多投射则不形成，从而促成所谓的旁分泌或容积传递。血清素能投射参与不同功能（运动、躯体感觉、边缘系统）系统的调节；并与广泛的神经精神和神经疾病相关。最后，最近的实验数据支持血清素在调节大脑发育中的作用，因此生命早期血清素能传递功能障碍可能导致长期的结构和功能改变。
