Département de Neurobiologie des Rythmes, Institut des Neurosciences Cellulaires et Intégratives, CNRS UPR-3212, 5 rue Blaise Pascal, 67084 Strasbourg, France.
Eur J Neurosci. 2009 Nov;30(9):1790-801. doi: 10.1111/j.1460-9568.2009.06986.x. Epub 2009 Oct 26.
The Syrian hamster (Mesocricetus auratus) is a widely used species for the study of biological clock synchronization and photoperiodism. The serotoninergic system arising from the median (MnR) and the dorsal raphé (DR) is a major actor in circadian clock synchronization. This serotoninergic system is also associated with functions and behaviours influenced by seasonal changes. The aim of the present study was to assess the influence of photoperiod on the daily functioning of the MnR and DR serotoninergic system. The morphology of both raphé nuclei was analysed in hamsters kept under long and short photoperiod by immunocytochemical detection of two markers of the serotoninergic system, serotonin and tryptophan hydroxylase (TPH, the rate-limiting enzyme of serotonin synthesis). The morphological analysis revealed a fairly complex morphological organization of the DR and MnR along their caudo-rostral extent. This morphological organisation was similar in the two photoperiods. However, quantification of several markers of serotonin (5-HT) synthesis in the DR and MnR revealed a time-dependent functioning of serotoninergic cells that was locally influenced by photoperiod. In particular, the significant daily variations of tph2-mRNA and TPH levels in the rostral MnR, and of the 5-HT/5-HIAA (5-hydroxyindoleacetic acid) ratio within the suprachiasmatic nuclei, were abolished under short photoperiod. The results are discussed with regard to the known physiological role of the serotoninergic system on the biological clock.
叙利亚仓鼠（Mesocricetus auratus）是一种广泛用于生物钟同步和光周期研究的物种。从中缝（MnR）和背侧中缝（DR）产生的 5-羟色胺能系统是生物钟同步的主要因素。这个 5-羟色胺能系统也与受季节变化影响的功能和行为有关。本研究旨在评估光周期对 MnR 和 DR 5-羟色胺能系统日常功能的影响。通过对两种 5-羟色胺能系统标志物——5-羟色胺和色氨酸羟化酶（TPH，5-羟色胺合成的限速酶）的免疫细胞化学检测，分析了在长光照和短光照下保持的仓鼠的中缝核和背侧中缝核的形态。形态分析显示，DR 和 MnR 在其尾到头的延伸方向上具有相当复杂的形态组织。这种形态组织在两种光周期下是相似的。然而，对 DR 和 MnR 中几种 5-羟色胺（5-HT）合成标志物的定量分析显示，5-羟色胺能细胞的功能具有时间依赖性，并且受到光周期的局部影响。特别是，在短光照下，MnR 前部的 tph2-mRNA 和 TPH 水平以及视交叉上核内 5-HT/5-HIAA（5-羟吲哚乙酸）比值的显著日变化被消除。结果与 5-羟色胺能系统对生物钟的已知生理作用进行了讨论。
