Neural mechanisms of sleep loss in Mexican cavefish

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General AbstractWhile sleep is nearly universal in the animal kingdom, the biological factors regulating sleep remain unclear. Sleep duration varies greatly between individuals, but little is known about how variation in brain chemistry may underlie differences in sleep need. To learn more about how brain chemistry affects sleep need, a group of fish that have lost the need to sleep during their evolution are being studied. Mexican cavefish were trapped in caves millions of years ago, and have since adapted to these nutrient-poor environments by dramatically reducing sleep, though we do not yet know what changes in the brain make that possible. Work in this project tests if changes in sleep need are associated with alterations sensory processes that promote the production of a chemical called Orexin. Orexin production in the brain is being compared between cavefish and related, river-dwelling surface fish with regular sleep patterns, and the ability of drugs that influence Orexin to alter sleep in cavefish is also being examined. Determining the chemical basis for sleep loss in Mexican cavefish will enable us to better understand how the brain normally regulates sleep, as well as how changes in brain chemistry, across evolutionary time or day-to-day in animals that need sleep, affect this critical life function and an animal's well-being. Numerous undergraduates from diverse racial and socioeconomic groups will participate in this work, as well as in developing community outreach programs that will use enhance scientific literacy in the public at large and in senior citizen communities in particular.Technical AbstractSleep is a nearly ubiquitous behavior throughout the animal kingdom, yet little is known about the functional and evolutionary principles driving sleep differences between species or individuals within a population. The Mexican cavefish Astyanax mexicanus, exists as independent populations of an ancestral eyed surface morph and blind cave morphs of the same species. The convergent evolution of sleep loss in multiple independent A. mexicanus cave populations provides the unique opportunity to examine the role of ecology and evolutionary history in shaping sleep. This research program will determine whether sensory input through the lateral line directly modulates function of the wake-promoting neuropeptide Orexin and the contributions of changes in Orexin neuroanatomy to the evolution of sleep loss in cave populations. Work produced in this project will contribute to our understanding of the biological basis of sleep with potential extension to a better understanding of the mechanistic basis of naturally occurring sleep differences in humans. In addition to contributing to scientific knowledge across life disciplines, this project will provide opportunities for student training and outreach in the local community. Teaching tools will be developed in collaboration with a local high school to expose students to behavioral ecology and neuroscience research. All developed lab protocols will be made available online for access and use at other high schools and teaching institutions. Additionally, this project will fund students enrolled in programs for first generation and minority college students to work in the research laboratory.