Steel Colin G H, Vafopoulou Xanthe
Department of Biology, York University, 4700 Keele St., Toronto, Ontario, Canada M3J 1P3.
Comp Biochem Physiol A Mol Integr Physiol. 2006 Jul;144(3):351-64. doi: 10.1016/j.cbpa.2006.02.018. Epub 2006 Mar 6.
This review presents a new perspective on the circadian regulation and functions of insect developmental hormones. In Rhodnius prolixus (Hemiptera), the brain neuropeptide prothoracicotropic hormone (PTTH) is released with a circadian rhythm that is controlled by paired photosensitive clocks in the brain. These clocks comprise the dorsal and lateral PER/TIM clock neurons known to regulate behavioral rhythms in Drosophila. Axons of PTTH and clock cells make close contact. Photosensitive PER/TIM clocks also reside in the paired prothoracic glands (PGs), which generate rhythmic synthesis and release of the ecdysteroid molting hormones. The PG clocks are entrained by both light and PTTH. These four clocks are coupled together by both nerves and hormones into a timing system whose primary regulated output is the circadian rhythm of ecdysteroids in the hemolymph. This complex timing system appears necessary to ensure circadian organization of the gene expression that is induced in target cells by ecdysteroids via circadian cycling of the nuclear ecdysteroid receptor (EcR). This multioscillator system serves to transduce 'the day outside' into endocrine rhythms that orchestrate 'the day inside'. It has many functional similarities with vertebrate circadian systems.
本综述提出了关于昆虫发育激素昼夜节律调节及其功能的新观点。在红带锥蝽（半翅目）中，脑源神经肽促前胸腺激素（PTTH）以昼夜节律释放，该节律由脑中一对光敏时钟控制。这些时钟由已知调节果蝇行为节律的背侧和外侧PER/TIM时钟神经元组成。PTTH和时钟细胞的轴突紧密接触。光敏PER/TIM时钟也存在于成对的前胸腺（PGs）中，前胸腺产生蜕皮甾体蜕皮激素的节律性合成和释放。PG时钟受光和PTTH两者的调节。这四个时钟通过神经和激素耦合在一起，形成一个计时系统，其主要调节输出是血淋巴中蜕皮甾体的昼夜节律。这个复杂的计时系统似乎对于确保蜕皮甾体通过核蜕皮甾体受体（EcR）的昼夜循环在靶细胞中诱导的基因表达的昼夜组织是必要的。这个多振荡器系统用于将“外部的一天”转化为协调“内部的一天”的内分泌节律。它与脊椎动物的昼夜节律系统有许多功能上的相似之处。
