Yoshimura T, Yasuo S, Suzuki Y, Makino E, Yokota Y, Ebihara S
Division of Biomodeling, Graduate School of Bioagricultural Sciences, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, 464-8601, Japan.
Am J Physiol Regul Integr Comp Physiol. 2001 Apr;280(4):R1185-9. doi: 10.1152/ajpregu.2001.280.4.R1185.
Circadian rhythms are generated by an internal biological clock. The suprachiasmatic nucleus (SCN) in the hypothalamus is known to be the dominant biological clock regulating circadian rhythms in mammals. In birds, two nuclei, the so-called medial SCN (mSCN) and the visual SCN (vSCN), have both been proposed to be the avian SCN. However, it remains an unsettled question which nuclei are homologous to the mammalian SCN. We have identified circadian clock genes in Japanese quail and demonstrated that these genes are expressed in known circadian oscillators, the pineal and the retina. Here, we report that these clock genes are expressed in the mSCN but not in the vSCN in Japanese quail, Java sparrow, chicken, and pigeon. In addition, mSCN lesions eliminated or disorganized circadian rhythms of locomotor activity under constant dim light, but did not eliminate entrainment under light-dark (LD) cycles in pigeon. However, the lesioned birds became completely arrhythmic even under LD after the pineal and the eye were removed. These results indicate that the mSCN is a circadian oscillator in birds.
昼夜节律由一个内部生物钟产生。已知下丘脑的视交叉上核（SCN）是调节哺乳动物昼夜节律的主要生物钟。在鸟类中，两个核团，即所谓的内侧SCN（mSCN）和视觉SCN（vSCN），都被认为是鸟类的SCN。然而，哪些核团与哺乳动物的SCN同源仍是一个未解决的问题。我们在日本鹌鹑中鉴定出了昼夜节律钟基因，并证明这些基因在已知的昼夜节律振荡器——松果体和视网膜中表达。在此，我们报告这些钟基因在日本鹌鹑、爪哇麻雀、鸡和鸽子的mSCN中表达，但在vSCN中不表达。此外，mSCN损伤消除或扰乱了持续昏暗光线下运动活动的昼夜节律，但并未消除鸽子在明暗（LD）循环下的昼夜节律调整。然而，在摘除松果体和眼睛后，即使在LD条件下，受损的鸟类也变得完全无节律。这些结果表明，mSCN是鸟类的一个昼夜节律振荡器。
