# Circadian Regulation of Zebrafish Sleep by Melatonin

> **NIH NIH R01** · CALIFORNIA INSTITUTE OF TECHNOLOGY · 2020 · $360,938

## Abstract

ABSTRACT
Sleep is regulated by homeostatic and circadian mechanisms. Several factors mediate homeostatic control of
sleep and mechanisms that regulate the circadian clock are well understood, but little is known about how the
circadian clock regulates sleep. Melatonin (MT) is a good candidate link between the circadian clock and sleep
because the circadian clock regulates its production, it can induce sleep in several diurnal species, including
humans, and its loss is associated with reduced sleep in humans. MT may play an ancient role in regulating
rest/activity states, as it does so in animals such as nematodes and zooplankton. However, the role of MT in
vertebrate sleep is controversial for two reasons. First, most nocturnal lab mouse strains do not synthesize MT,
yet they exhibit circadian control of sleep. However, MT synthesis peaks at night in both diurnal and nocturnal
animals, and MT does not induce sleep in nocturnal animals, suggesting that MT only regulates sleep in
diurnal animals. Second, a large number of studies in vertebrates have failed to show a consistent role for MT
in sleep, suggesting that it is not a central sleep regulator, but rather has species-specific roles. However,
these studies used pinealectomy (Px), a crude, imprecise and invasive procedure that does not address the
function of MT in a clean manner. Thus, it is likely that distinct effects of Px result from differences in the Px
procedure in different species and in different labs. The pineal gland also likely has functions in addition to MT
production, so Px may cause effects that obscure MT-dependent phenotypes. These confounds are avoided
by using genetics to create MT-deficient animals. We have addressed this question using zebrafish, a diurnal
vertebrate that exhibits behavioral, anatomical, genetic and pharmacological conservation of mammalian
sleep. We found that circadian regulation of sleep is abolished in zebrafish that lack MT due to mutation of
arylalkylamine N-acetyltransferase (aanat2). This finding suggests that MT mediates the circadian regulation
of sleep in a diurnal vertebrate and provides a basis to explore genetic and neurological mechanisms through
which the circadian system and MT regulate sleep. In Specific Aim 1 we use genetics to determine which MT
receptors are required for circadian regulation of sleep and for sleep induced by exogenous MT. In Specific
Aim 2 we identify neurons that are activated or inhibited in response to exogenous MT and in MT-deficient
animals using cfos in situ hybridization and whole-brain GCaMP6s calcium imaging. In Specific Aim 3 we use
genetics and mass spectrometry to test the hypothesis that MT promotes sleep by stimulating adenosine
signaling. If correct, this would suggest a simple mechanism that integrates homeostatic and circadian control
of sleep. This project will help to reveal how MT, and thus the circadian clock, regulates sleep in a diurnal
vertebrate. Sleep disorders are common, have poor therapeu...

## Key facts

- **NIH application ID:** 9879771
- **Project number:** 5R01NS101665-09
- **Recipient organization:** CALIFORNIA INSTITUTE OF TECHNOLOGY
- **Principal Investigator:** David Aaron Prober
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2020
- **Award amount:** $360,938
- **Award type:** 5
- **Project period:** 2017-04-01 → 2021-03-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/9879771

## Citation

> US National Institutes of Health, RePORTER application 9879771, Circadian Regulation of Zebrafish Sleep by Melatonin (5R01NS101665-09). Retrieved via AI Analytics 2026-05-21 from https://api.ai-analytics.org/grant/nih/9879771. Licensed CC0.

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