RUI: Ionic Conductances Underlying Serotonergic Modulation of Rhythmic Motor Behavior

神经系统最重要的功能之一是控制运动。走路、游泳和飞行都是有节奏的运动行为的例子，它们由一种相对刻板的肌肉收缩模式组成。为了生存，动物还必须能够调整自己的运动和其他行为，以适应不断变化的环境。例如，作为对日益增加的饥饿感的反应，动物可能会增加给定的感官刺激的可能性，比如发现潜在的猎物，这会导致运动行为的激活，使动物向猎物移动。因此，神经生物学的一个重要目标是了解运动行为背后的神经回路是如何随着时间而改变的。在无脊椎动物和脊椎动物中实现回路功能改变的一种方法是用一种叫做神经调节剂的化学物质改变神经元的电和突触特性。在运动行为的神经调节剂中，研究得最多的是一种叫做血清素的化学物质。本项目将研究血清素对药蛭运动神经元控制游泳行为的影响。由于相对简单，水蛭是少数几种能够追踪到从感觉输入到产生节奏的回路，再到产生实际动作的肌肉的连续路径的生物之一。饥饿的水蛭神经元周围的血液中血清素水平更高，因此更有可能游泳。此外，血清素影响游泳行为通路中几种神经元的电特性。然而，目前还不清楚血清素是如何影响这些神经元，从而增加游泳的可能性的。这些信息将通过在受控条件下直接测量水蛭接触血清素前后游动运动神经元中的离子电流来获得。在确定了由血清素修饰的离子电流后，将确定这种神经调节剂引起的具体变化。将结果数据与各种无脊椎动物和脊椎动物的运动行为调节研究进行比较，将有助于阐明包括人类在内的所有动物运动行为控制的一般原理。

JAMES D. ANGSTADT - PROJECT SUMMARYIonic Conductances Underlying Serotonergic Modulation of Rhythmic MotorBehavior One of the most important functions of the nervous system is to control movement. Walking, swimming and flying are examples of rhythmic motor behaviors that consist of a relatively stereotyped pattern of muscle contractions. To survive, an animal must also be able to modify its motor and other behaviors to meet the demands of a changing environment. In response to increasing hunger, for example, an animal may increase the probability that a given sensory stimulus, such as detection of potential prey, will lead to activation of motor behaviors that move the animal toward the prey. Thus, an important goal in neurobiology is to understand how the neural circuits underlying motor behavior are modified over time. One way that changes in circuit function are achieved in both invertebrate and vertebrate animals is to alter the electrical and synaptic properties of neurons with chemicals called neuromodulators. One of the most well studied neuromodulators of motor behavior is a chemical called serotonin. In this project, the effects of serotonin on motor neurons controlling swimming behavior in the medicinal leech will be examined. Because of its relative simplicity, the leech is one of only a handful of organisms in which it has been possible to trace a continuous pathway from sensory input to the rhythm-generating circuit and then out to the muscles that generate the actual movements. Hungry leeches have higher levels of serotonin in the blood surrounding their neurons and, as a result, are more likely to swim. Moreover, serotonin affects the electrical properties of several types of neurons found in the swim behavior pathway. However, it is not yet understood exactly how serotonin affects these neurons to cause the increased probability of swimming. This information will be obtained by measuring directly, under controlled conditions, the ionic currents in swim motor neurons of the leech before and after exposure to serotonin. After identifying those ionic currents modified by serotonin, the specific changes induced by this neuromodulator will be identified. Comparison of the resulting data with research on modulation of motor behaviors in a variety of invertebrate and vertebrate species will contribute to the elucidation of general principles underlying the control of motor behavior in all animals, including humans.