Xu Z Q, Hökfelt T
Department of Neuroscience, Karolinska Institute, Stockholm, Sweden.
J Chem Neuroanat. 1997 Aug;13(3):169-87. doi: 10.1016/s0891-0618(97)00043-4.
The dorsal raphe nucleus (DR) of the rat was studied with triple labeling immunofluorescence histochemistry to evaluate the quantitative relationships between neurons expressing 5-hydroxytryptamine (5-HT), the neuropeptide galanin (GAL) and the nitric oxide (NO) synthesizing enzyme NO synthase (NOS). In addition retrograde tracing studies were performed. It could be established that a high percentage (between 40 and 60%) of the 5-HT neuron profiles in the ventromedial and dorsomedial subgroups of the DR contained both GAL and NOS after colchicine treatment. This triple coexistence was lower in the dorso-lateral subgroup and much lower in the lateral subgroup (down to 5%). All GAL neuron profiles contained 5-HT, and they constituted up to 80% of all labeled profiles in the rostral ventromedial and caudal dorsomedial subgroups, with the lowest percentage in the lateral subgroup (45%). The percentage of 5-HT-alone neuron profiles in these four subgroups varied between 15-40%. The proportion of 5-HT/NOS neurons was low (a few percent) at all levels, and this was the case also for NOS-alone neuron profiles except in the lateral subgroup, where 10-20% were of this type. It could be established that some 5-HT/GAL/NOS neurons project to the striatum. These retrogradely labeled cells were mainly found in the mid-line subgroups. In the striatum a moderately dense 5-HT fiber network and numerous NOS-positive cell bodies and fibers could be observed. However, only a few, weakly fluorescent GAL fibers were found and in a small number of cases it could be shown or was likely that 5-HT and GAL coexisted. No evidence for coexistence between 5-HT and NOS was obtained. The present findings strongly suggest that a large proportion of the DR 5-HT neurons can synthesize and release two additional messenger molecules, GAL and NO. Furthermore, even if the 5-HT/GAL/NOS neurons project to the striatum, the amounts of GAL and NOS transported to the terminal ramifications in this area are very low. This is in agreement with a very low GAL synthesis in the DR under normal circumstances, which is also indicated by the fact that colchicine treatment is needed to visualize GAL-like immunoreactivity in DR cell bodies. It is possible that NO, and perhaps GAL, in 5-HT neurons exert their main actions at the somatic and dendritic level in the DR.
采用三重标记免疫荧光组织化学方法对大鼠背侧中缝核（DR）进行研究，以评估表达5-羟色胺（5-HT）、神经肽甘丙肽（GAL）和一氧化氮（NO）合成酶一氧化氮合酶（NOS）的神经元之间的定量关系。此外，还进行了逆行追踪研究。结果表明，秋水仙碱处理后，DR腹内侧和背内侧亚组中40%至60%的5-HT神经元轮廓同时含有GAL和NOS。这种三重共存现象在背外侧亚组中较低，在外侧亚组中更低（低至5%）。所有GAL神经元轮廓都含有5-HT，在吻侧腹内侧和尾侧背内侧亚组中，它们占所有标记轮廓的比例高达80%，在外侧亚组中比例最低（45%）。这四个亚组中仅含5-HT的神经元轮廓比例在15%至40%之间。5-HT/NOS神经元的比例在所有水平都很低（百分之几），仅含NOS的神经元轮廓也是如此，除了外侧亚组，该亚组中此类神经元占10%至20%。可以确定，一些5-HT/GAL/NOS神经元投射到纹状体。这些逆行标记的细胞主要见于中线亚组。在纹状体中，可以观察到中等密集的5-HT纤维网络以及大量NOS阳性细胞体和纤维。然而，仅发现少量弱荧光的GAL纤维，在少数情况下可以显示或可能显示5-HT和GAL共存。未获得5-HT和NOS共存的证据。目前的研究结果强烈表明，DR中很大一部分5-HT神经元能够合成并释放另外两种信使分子GAL和NO。此外，即使5-HT/GAL/NOS神经元投射到纹状体，转运到该区域终末分支的GAL和NOS量也非常低。这与正常情况下DR中GAL合成非常低的情况一致，秋水仙碱处理才能使DR细胞体中的GAL样免疫反应性可视化这一事实也表明了这一点。5-HT神经元中的NO，可能还有GAL，可能在DR的胞体和树突水平发挥其主要作用。
