Cayetanot Florence, Deprez Julien, Aujard Fabienne
Adaptive Mechanisms and Evolution, CNRS-MNHN UMR 7179, Brunoy, France.
Eur J Neurosci. 2007 Oct;26(7):2025-32. doi: 10.1111/j.1460-9568.2007.05826.x.
In mammals, the suprachiasmatic nucleus (SCN) of the hypothalamus is the master circadian pacemaker. The SCN controls daily rhythms and synchronizes the organism to its environment and especially to photic signals. Photic signals via the retinohypothalamic tract reach the ventral part of the SCN, where the majority of calbindin-containing neurons are located. Calbindin cells seem important for the control of circadian rhythmicity. As ageing leads to marked changes in the expression of circadian rhythms, we investigated in the mouse lemur, a nocturnal primate, age-related changes in the oscillation of calbindin protein expression in SCN neurons. We used immunohistochemistry and quantitative analysis of calbindin expression in the SCN of adult and aged mouse lemurs. In this primate, a dense cluster of calbindin-positive neurons was found in the ventral part of the SCN. In adult animals, calbindin-positive SCN neurons did not exhibit daily rhythms in their number or intensity, but exhibited significant daily variations in the percentage of cells with a calbindin-positive nucleus, characterized by high values during the daytime and low values during the night. Immunoreactive intensity peaked in the middle of the daytime. Calbindin expression in the nuclei of calbindin cells in the SCN tends to be modified by ageing. The amplitude of daily variation in calbindin expression was damped, with a lower immunointensity during the daytime and a delayed decrease during the night. These changes may affect the ability of the SCN to transmit rhythmic information to other SCN cells and thereby modify the synchronization of the different cell populations in the SCN.
在哺乳动物中，下丘脑的视交叉上核（SCN）是主要的昼夜节律起搏器。SCN控制日常节律，并使生物体与环境同步，尤其是与光信号同步。通过视网膜下丘脑束的光信号到达SCN的腹侧部分，这里是大多数含钙结合蛋白神经元所在的位置。钙结合蛋白细胞似乎对昼夜节律的控制很重要。由于衰老会导致昼夜节律表达的显著变化，我们在夜间活动的灵长类动物小鼠狐猴中研究了SCN神经元中钙结合蛋白蛋白表达振荡的年龄相关变化。我们使用免疫组织化学和对成年和老年小鼠狐猴SCN中钙结合蛋白表达的定量分析。在这种灵长类动物中，在SCN的腹侧部分发现了一簇密集的钙结合蛋白阳性神经元。在成年动物中，钙结合蛋白阳性的SCN神经元在数量或强度上没有表现出每日节律，但在具有钙结合蛋白阳性细胞核的细胞百分比上表现出显著的每日变化，其特征是白天值高，夜间值低。免疫反应强度在白天中间达到峰值。SCN中钙结合蛋白细胞的细胞核中的钙结合蛋白表达往往会因衰老而改变。钙结合蛋白表达的每日变化幅度减小，白天免疫强度较低，夜间下降延迟。这些变化可能会影响SCN向其他SCN细胞传递节律信息的能力，从而改变SCN中不同细胞群的同步性。
