Autonomic control of cardiac output in teleost fishes

脊椎动物生活在多种环境中，维持体内恒定状态的系统进化对它们的生存至关重要。当心血管需求发生变化，心脏泵出的血容量需要调整时，循环系统提供氧气和营养来保持身体组织的活力。这是由排列在自主神经系统回路中的神经元精确而迅速地控制的。然而，我们对这些神经回路如何在脊椎动物中运作的了解还不完整。在这里，我建议研究这种控制是如何在硬骨鱼的心脏中起作用的，硬骨鱼代表了脊椎动物心脏功能的祖先原型。心脏泵出多少血的主要因素是它跳动的速度。心脏起搏器细胞通过产生收缩的电信号来设定心率。起搏器的频率是由神经控制的，但在鱼类中，无论是起搏器细胞的详细位置，还是控制心率的电路，都没有得到很好的理解。在这项研究中，我将使用斑马鱼，一种研究广泛器官功能，遗传学和胚胎发育的模型脊椎动物，来研究心脏的三个方面。1)起搏器细胞的位置和速率设定特性是什么？这些细胞是如何被控制的？我开发了一种新的制备方法，使斑马鱼的心脏在培养皿中分离后有规律地跳动。有了这个，我现在已经定位了起搏器区，并将建立在那里产生心律的细胞的特性。我将确定哪些神经系统成分以起搏器细胞为目标，以及这些成分是如何组织起来影响心率的。这部分研究的结果将显示涉及心脏神经调节的操作原理。2)在开发过程中心脏的控制是如何产生的？理解心脏运作原理的一个关键部分是神经系统和心脏在发育过程中是如何整合在一起的。我将通过探索斑马鱼卵和幼体心脏内神经系统的解剖结构和功能来研究这一点，因为心脏成熟了，可以满足不断增长的氧气和营养的输送需求。3)上述研究在斑马鱼身上的发现是否能更广泛地应用于硬骨鱼类？在研究任何一个物种的生物系统时，有可能这些发现只局限于该物种，或者只适用于一小群相关动物。为了检验上述研究的结果是否在鱼类中具有普遍性，我将在日本的medaka中重复这些研究，medaka是一组比斑马鱼进化晚得多的鱼类的代表。因此，除了提出的工作的直接结果之外，我的结果将对我们对自主神经系统如何作用于脊椎动物心脏以控制其功能的理解产生重大影响。

Vertebrates live in many environments, and the evolution of systems for maintaining a constant internal body state has been critical for their survival. The circulatory system provides oxygen and nutrients to keep body tissues alive as cardiovascular demands change and the blood volume pumped by the heart needs adjustment. This is precisely and rapidly controlled by neurons arranged in circuits in the autonomic nervous system. Yet our knowledge of how these circuits operate in any vertebrate is incomplete. Here I propose to investigate how such control works in the hearts of bony fishes, representing the ancestral prototype for cardiac function in vertebrates. The main factor in how much blood the heart pumps is how fast it beats. Cardiac pacemaker cells set heart rate by generating the electrical signal for contraction. The pacemaker rate is under neural control, but in fishes neither the detailed location of pacemaker cells, nor the circuits controlling heart rate, is well understood. In this study I will use the zebrafish, a model vertebrate for investigating a wide range of organ function, genetics and embryological development, to study 3 aspects of the heart. 1) What is the site and the rate-setting properties of pacemaker cells and how are these cells controlled? I have developed a new preparation of the zebrafish heart that beats regularly after isolation in a dish. With this I have now located the pacemaker zone, and will establish the properties of cells there that generate the heart rhythm. I will determine which components of the nervous system target pacemaker cells, and how these components are organized to influence heart rate. The results of this part of the study will show the operating principles involved in nervous regulation of the heart. 2) How does the control of the heart arise during development? A key component in understanding the operating principles of the heart is how the nervous system and heart become integrated during development. I will study this by probing the anatomy and function of the nervous system within the hearts of zebrafish eggs and larvae as the heart matures to meet ever-increasing requirements for delivering oxygen and nutrients. 3) Will the findings in zebrafish from the above studies apply more broadly across bony fishes? In studying biological systems in any one species, it is possible that the findings might be limited to just that species, or may apply only to a small group of related animals. To test whether the results of the studies described above may be general among fishes, I will repeat these studies in the Japanese medaka, representative of a group of fishes that evolved much later than zebrafish. Thus, beyond the immediate outcome of the proposed work, my results will have a major impact on our understanding of how the autonomic nervous system acts on the vertebrate heart to control its function.