Finding time for dinner: real-time bioluminescence reporting of circadian gene expression in food-entrained rodents

哺乳动物的行为和生理是由大脑和周围器官和组织中的内源性昼夜节律时钟（24小时）调节的。这些生物钟产生每天的睡眠、觉醒、食欲和体温节律，并协调所有器官系统的功能，配合每天的昼夜循环和进餐时间。位于下丘脑的主昼夜节律时钟对于使日常节律与昼夜周期同步至关重要，但仅间接参与每日进餐时间的同步。我们的研究旨在了解日常行为和生理节奏与可预测的日常用餐时间同步的大脑机制。分子生物学在昼夜节律计时方面的最新进展已经确定了许多表现出昼夜节律表达的基因，并形成连锁的负反馈和正反馈循环，产生自我维持的细胞自主节律。现在有了转基因大鼠和小鼠，其中萤火虫荧光素酶基因已经与这些生物钟基因之一的启动子融合在一起，这样当生物钟基因表达时，大脑和器官组织就会发光。从特定的大脑区域和周围器官中提取的组织可以在培养中保存数周，在此期间，可以通过光度法连续实时测量生物发光。我们将用这笔设备拨款购买一个测光系统，用它我们将解决有关产生食物同步日常节奏的大脑系统组织的基本问题。具体目标将是1。确定控制与食物同步的行为、自主神经和内分泌节律的生物钟在大脑（或外围）中的位置。2 .确定每日进餐时间的节律同步是否涉及单个或多个时钟系统；确定喂养和禁食的时间如何影响昼夜节律的重置速度，以响应日常明暗周期的变化。这些信息将帮助我们了解大脑是如何调节日常节律的，以及如何利用进餐时间来最大限度地减少昼夜交替对昼夜节律的破坏。

The behaviour and physiology of mammals is regulated by endogenous circadian (24 h) clocks in the brain and in peripheral organs and tissues. These clocks generate daily rhythms of sleep-wake, appetite and body temperature and coordinate the functions of all organ systems with daily cycles of light-dark and mealtimes. A master circadian clock located in the hypothalamus is critical for synchronizing daily rhythms to light-dark cycles, but is only indirectly involved in synchrony to daily mealtimes. Our research aims to understand the brain mechanisms by which daily rhythms of behaviour and physiology are synchronized to predictable daily mealtimes. Recent advances in the molecular biology of circadian timekeeping have identified a number of genes that exhibit circadian rhythms of expression, and that form interlocking negative and positive feedback loops that produce self-sustaining, cell autonomous rhythmicity. Transgenic rats and mice are now available in which the firefly luciferase gene has been fused with the promotor of one of these circadian clock genes, such that brain and organ tissues emit light when the clock gene is expressed. Tissue from specific brain regions and peripheral organs can be extracted and maintained for many weeks in culture, during which bioluminescence can be measure continuously, in real time, by photometry. We will use this equipment grant to purchase a photometry system with which we will address fundamental questions about the organization of the brain system that generates food-synchronized daily rhythms. Specific objectives will be to 1. determine the location in the brain (or periphery) of the circadian clocks that control food-synchronized behavioral, autonomic and endocrine rhythms, 2. determine whether synchrony of rhythms to 2 or more daily mealtimes involves a single or a multiple clock system, and 3. determine how the timing of feeding and fasting affects the rate at which circadian rhythms reset in response to a shift of the daily light-dark cycle. This information will help us understand how the brain regulates daily rhythms, and how meal timing may be used to minimize disruption of circadian timekeeping following shifts of light-dark.