We describe, for the first time, the effects of the wakefulness-promoting drug modafinil on sleep and wakefulness in larval zebrafish. Modafinil is currently used to treat narcolepsy, hypersomnia, and shift-work disorder by increasing wakefulness. Tolerance and dependence are limited with modafinil use, differentiating it from common stimulants; however, the neural mechanisms of action of modafinil are still unknown. Zebrafish, a low-cost, prolific, and genetically tractable animal model, have recently become a key model in sleep research. Zebrafish express circadian rhythms, sleep homeostasis, and sleep pressure, and, in addition, respond to common hypnotics and stimulants in a manner similar to mammals. Therefore, in the current experiment we characterize the effects of modafinil on sleep-wake cycles in larval zebrafish as a first step to gaining further insight into the neural mechanisms underlying the effects of modafinil. We show that modafinil modulates sleep-wake activity in larval zebrafish in a manner consistent with what would be predicted from mammalian data. Modafinil increases wakefulness by lengthening wake-bouts, an effect that likely restricted to the night (lights-off). These results validate the use of zebrafish as an animal model for the study of sleep and provide a means for dissecting the neural mechanisms of modafinil, and, more broadly, sleep disorders.

Recently, the zebrafish (Danio rerio) has been established as a key animal model in neuroscience. Behavioral, genetic, and immunohistochemical techniques have been used to describe the connectivity of diverse neural circuits. However, few studies have used zebrafish to understand the function of cerebral structures or to study neural circuits. Information about the techniques used to obtain a workable preparation is not readily available. Here, we describe a complete protocol for obtaining in vitro and in vivo zebrafish brain preparations. In addition, we performed extracellular recordings in the whole brain, brain slices, and immobilized nonanesthetized larval zebrafish to evaluate the viability of the tissue. Each type of preparation can be used to detect spontaneous activity, to determine patterns of activity in specific brain areas with unknown functions, or to assess the functional roles of different neuronal groups during brain development in zebrafish. The technique described offers a guide that will provide innovative and broad opportunities to beginner students and researchers who are interested in the functional analysis of neuronal activity, plasticity, and neural development in the zebrafish brain.