The circadian oscillator organization underlying the regulation of goal directed behaviour in mammals

我们研究项目的主要目的是了解哺乳动物的昼夜节律是如何在不同层次的生物组织（分子、细胞和电路）中产生的，它们是如何共同产生生理和行为的日常时间程序的。两个相互作用的时钟的活动在小鼠的运动活动中是明显的。其中之一是下丘脑（SCN）中的生物钟。另一个还没有本地化，但是当遇到环境中的重大事件或条件时，它对于产生对日常活动时间的短期调整很重要。特别是，第二个时钟与预测重要情况的能力有关，比如食物的可用性或捕食者的存在。为了做到这一点，生物钟必须将一天中的时间传达给动物的其他部分，以预测事件再次发生。这是时间记忆。我们将研究目标导向的行为，如跑轮活动，因为这可能是自然探索行为的替代品。目前的研究结果表明，生物钟是由多巴胺调节的，这表明节律可能是由神经回路产生的。我们简单地把这种输出称为多巴胺调节的昼夜节律振荡（DARCO）。我们的数据表明，时间记忆反映在DARCO电路的设置上。该项目有两个主要假设，每个假设都有几个目标。***假设1：安非他明诱导的DARCO出现在一个回路中，包括上升多巴胺通路和谷氨酸/GABA反馈。为了验证这一点，我们将首先开发和测试一个描述两个时钟相互作用的数学模型。其次，电路有已知的元件，我们将以两种方式进行测试。将使用特定的药物来检查电路中的细胞如何交流。此外，选定的途径将被改造以产生可用于打开或关闭这些细胞活动的蛋白质。第二个假设是，SCN通过白天活跃的神经连接抑制多巴胺细胞的活动。***假设2:SCN通过抑制投射到下丘脑后部来调节DARCO。***为了验证这一假设，我们将首先使用通道追踪技术验证路径的实际存在。然后，我们将研究这一途径的功能，通过工程抑制或兴奋蛋白进入这些神经元，并控制它们的活动。***总之，该研究将告知(1)时钟如何在目标导向行为中产生DARCO节奏；(2)自然情况下SCN时钟如何控制DARCO。这项研究的主要影响将是扩大我们对昼夜节律层次的组织和意义的理解。我们的项目提出了一个迄今为止未被探索的机制，从分子到电路，生物体已经适应了24小时环境中的生活。

The broad aim of our research program is to understand how circadian rhythms in mammals that are produced at different levels of biological organization (molecules, cells, and circuits), come together to produce the daily temporal program of physiology and behavior. The activity of two interacting clocks is evident in the locomotor activity of mice. One of these is the biological clock in the hypothalamus (the SCN). The other has not been localized, but it is important for producing short-term adjustments to the daily timing of activity when significant events or conditions n the environment are encountered. In particular, the second clock is connected with the ability to predict important conditions such as the availability of food or the presence of a predator. To do this, the clock must communicate time of day to the rest of the animal in anticipation of the event occurring again. This is time memory. We will examine goal directed behaviors such as running wheel activity, as this likely serves as a surrogate for exploratory behavior in nature. Current findings indicate that the clock is regulated by dopamine, which suggests that rhythms could be produce by neural circuit. We have simply called the output a dopamine regulated circadian oscillation, or DARCO. Our data suggest that time memory is reflected in the setting of the DARCO circuit.***The project has two main hypotheses and several objectives within each.***Hypothesis 1: The amphetamine-induced DARCO arises in a circuit that includes the ascending dopamine pathways and glutamate/GABA feedback.***To test this, we will first develop & test a mathematical model that describes the interactions of two clocks. Second, the circuit has known components that we will test in two ways. Specific drugs will be used to examine how cells in the circuit communicate. In addition selected pathways will be engineered to produce proteins that can be used to turn activity on or off in those cells. The second hypothesis is that the SCN inhibits activity in the dopamine cells by a neural connection that is active during the daytime. ***Hypothesis 2: The SCN regulates the DARCO via an inhibitory projection to posterior hypothalamus.***To test this hypothesis we will first verify that a pathway actually exists using tract tracing techniques. Then we will investigate the functionality of this pathway by engineering the inhibitory or excitatory proteins into those neurons, and controlling their activity.***Together, the research will inform about (1) how the clock generates the DARCO rhythm in the goal directed behavior; and (2) how the SCN clock controls the DARCO under natural situations. the major impact of this research will be to expand our understanding of the organization and significance of the circadian hierarchy. Our project presents a heretofore unexplored perspective on the mechanisms from molecules to circuits, by which living organisms have adapted to life in the 24 hr environment.