DISSERTATION RESEARCH: Melatonin Regulation of Vocal Behavior

昼夜节律近似于24小时的昼夜循环，使动物的行为和生理与环境线索的周期性变化同步，如光线，温度和配偶的可用性。生物节律是如何由荷尔蒙、遗传和神经机制产生的，这是一个很有科学意义的问题。夜间激素褪黑激素在将日常活动带入昼夜循环中起着核心作用。在许多哺乳动物中，活动和交配发生在晚上，因此褪黑激素有可能调节重要的生殖行为，如求爱时的发声。本研究将探讨昼夜节律和褪黑激素对一种高发声能力的平鳍鱼（Porichthys notatus）发声行为的日常节律的调节，并回答三个问题：（1）日常发声节律是否受内部昼夜节律的控制？(2)褪黑激素刺激夜间发声行为吗？(3)褪黑激素是否调节发声脑区神经兴奋性的基因表达？这些研究将有助于预测褪黑激素调节其他物种的发声行为的比较框架，包括鸟类和哺乳动物，表现出不同的日常活动模式。更广泛地说，褪黑激素与睡眠、时差反应、自闭症和癫痫有关，这使得关于它如何影响社交和神经兴奋性的基础研究变得重要和广泛适用。这个项目将测试整体假设，即海军军官候补生的夜间求爱发声是昼夜节律控制和褪黑激素刺激。拟议的研究将（1）在恒定的外部光照条件下记录自然行为鱼类的发声，以测试内部产生的昼夜发声节律，（2）将褪黑激素植入鱼类，以测试褪黑激素对发声行为的调节，以及（3）通过检测褪黑素对正常人神经兴奋性相关基因表达的调节，更深入地了解褪黑素如何影响发声行为的日常节律。语音网络的特点如果海军军官候补生的日常发声节律处于内源性昼夜节律控制之下，则预测在正常光照条件下记录的节律将在恒定黑暗下持续约24小时。此外，如果海军军官候补生的发声行为依赖于褪黑激素作用，则预测在恒定光照下发声将减少或消除，表明消除褪黑激素产生，而在光照下补充外源性褪黑激素将挽救发声的发生。最后，研究人员预测褪黑激素会增加先前确定的已知影响神经兴奋性的候选基因的表达。这些基因编码三种类型的离子通道，并在夏夜收集的后脑发声核中表现出增加的表达，这是最大的自然发声行为。鉴于保守的候选基因的功能，在这个建议中探索，这样的机制可以提供翻译的夜间褪黑激素信号，以增加或减少神经兴奋性在夜间与昼夜动物，分别分子基础。该项目将培训来自不同背景的男女大学生，包括代表性不足的少数民族。研究结果将在开放获取的同行评审期刊、通过在线平台发表的热门文章、国家和国际会议以及地方科学外联活动中传播。

Circadian rhythms that approximate the 24 hr day-night cycle, synchronize animal behavior and physiology to cyclical changes in environmental cues, such as light, temperature, and the availability of mates. How biological rhythms are generated by hormonal, genetic, and neural mechanisms is of great scientific interest. The nocturnal hormone melatonin plays a central role in entraining daily activity to the day-night cycle. In many mammals, activity and mating occur at night so there is potential for melatonin to regulate important reproductive behaviors such as vocalizations used in courtship. This project will investigate circadian and melatonin regulation of daily rhythms in the vocal behavior of a nocturnally active and highly vocal fish, the plainfin midshipman (Porichthys notatus) by answering three questions: (1) Is the daily vocal rhythm under internal, circadian control? (2) Does melatonin stimulate nocturnal vocal behavior? (3) Does melatonin regulate gene expression underlying neural excitability in vocal brain regions? These studies will contribute to a comparative framework for predicting melatonin regulation of vocal behavior in other species, including birds and mammals that exhibit divergent daily activity patterns. More broadly, melatonin has been implicated in sleep, jetlag, autism and epilepsy, making basic research on how it affects social communication and neural excitability important and widely applicable. This project will test the overall hypothesis that the midshipman's nocturnal courtship vocalization is under circadian control and stimulated by melatonin. Proposed studies will (1) record vocalizations from naturally behaving fish under constant external light conditions to test for an internally generated circadian vocal rhythm, (2) implant fish with melatonin to test for melatonin regulation of vocal behavior, and (3) seek a deeper understanding of how melatonin influences daily rhythms in vocal behavior by examining its regulation of neural excitability-related gene expression in a well-characterized vocal network. If the midshipman daily vocal rhythm is under endogenous circadian control, it is predicted that rhythms recorded under a normal light regime will persist under constant darkness with a period of ~24 hr. Additionally, if midshipman vocal behavior is dependent on melatonin action, it is predicted that vocalizations will be reduced or abolished under constant light, shown to abolish melatonin production, while exogenous melatonin replacement under light will rescue the occurrence of vocalizations. Finally, the researchers predict that melatonin increases the expression of previously identified candidate genes known to affect neural excitability. These genes encode three types of ion channels and exhibit increased expression in a hindbrain vocal nucleus collected during the summer night, a time of maximal natural vocal behavior. Given conserved functions of the candidate genes explored in this proposal, such mechanisms could provide the molecular basis for translating the nocturnal melatonin signal to increase or decrease neural excitability in nocturnal versus diurnal animals, respectively. This project will train current and new undergraduates of both genders from diverse backgrounds, including underrepresented minorities. The results will be disseminated in open-access peer-reviewed journals, popular articles via online platforms, at national and international conferences, and at local science outreach events.