A study of putative brain circadiom oscillators in amphibians and fish

1.为了深入研究两栖动物和鱼类生物钟的分子机制，我们从日本蝾螈（Cynops pyrrhogaster）和香鱼（Plecoglossus altivels）中分别克隆了编码Per2和Per3、Clock和Bmall的部分cDNA.采用放射免疫分析法测定了蝾螈、香鱼和虹鳟鱼血浆褪黑激素的含量，结果表明，在光暗循环下，血浆褪黑激素的含量具有明显的日变化。在蝾螈，昼夜变化的血浆褪黑激素水平被取消无论是松果体切除术或双侧眼球摘除。在持续黑暗下，香鱼血浆褪黑激素水平呈现昼夜节律变化，而虹鳟没有.我们的特点和本地化褪黑激素受体在蝾螈的大脑。褪黑激素受体对褪黑激素具有高度特异性，具有皮摩尔亲和力。放射自显影研究显示在大脑中的分布不均匀，在视顶盖中观察到最高密度。通过使用突触带的数量， ...更多信息 松果体光感受器作为松果体生物钟的相位标记，我们发现每天注射褪黑激素可以诱导蝾螈的松果体生物钟和昼夜运动活动节律。我们用铝箔覆盖蝾螈的头骨，同时颠倒了明暗循环。蒙头动物的自发活动节律被带入到颠倒的明暗周期，而松果体突触带数目的节律几乎保持与原始节律相同的相位。这些数据表明，在光暗周期下，视网膜感知的光可以在没有松果体生物钟帮助的情况下携带大脑中的生物钟。研究了松果体切除对虹鳟鱼摄食活动昼夜节律的影响。松果体切除术影响的需求喂养活动，无论是光暗或恒定的光照条件下，表明松果体器官是不是必不可少的，以维持在大脑中的昼夜节律钟的功能。少

1. To obtain the insight on the molecular mechanisms of the circadian clock in amphibians and fish, we isolated partial cDNAs encoding Per2 from the Japanese newt (Cynops pyrrhogaster) and Per2, Per3, Clock and Bmall from the ayu (Plecoglossus altivels).2. Plasma melatonin levels in the newt, ayu and rainbow trout (Oncorhynchus mykiss) determined by radioimmuno-assay exhibited significant daily variation under light-dark cycles. In the newt, the day-night change in plasma melatonin level was abolished by either pinealectomy or bilateral ocular enucleation. Plasma melatonin levels exhibit circadian variation under constant darkness in the ayu but not in the rainbow trout.3. We characterized and localized melatonin receptors in the newt brain. The melatonin receptors are highly specific for melatonin with picomolar affinity. Autoradiographic studies revealed uneven distribution in the brain with the highest density observed in the optic tectum.4. By using the number of synaptic ribbon in … More the pineal photoreceptor as a phase marker of the pineal circadian clock, we showed that daily melatonin injections entrained the pineal circadian clock as well as circadian locomotor activity rhythm in the newt.5. We covered the newt's skull with aluminum foil and simultaneously reversed the light-dark cycle. Locomotor activity rhythm of the head-covered animals was entrained to the reversed light-dark cycle while the rhythm of pineal synaptic ribbon number remained almost the same phase as the original one. These data suggest that under light-dark cycle retinally perceived light can entrain the circadian clock in the brain without help from the pineal circadian clock.6. The effects of pinealectomy on circadian rhythms in the demand-feeding activity of the rainbow trout were examined. Pinealectomy affected the demand-feeding activity under neither light-dark nor constant light conditions, indicating that the pineal organ is not essential to maintain the function of the circadian clock in the brain. Less