Neuron
Volume 95, Issue 1, 5 July 2017, Pages 153-168.e6
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Article
Light-Dependent Regulation of Sleep and Wake States by Prokineticin 2 in Zebrafish

https://doi.org/10.1016/j.neuron.2017.06.001Get rights and content
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Highlights

  • Prok2 overexpression induces sleep in light and suppresses sleep in dark

  • Prok2-induced sleep is independent of circadian rhythms and requires prokr2

  • prok2 mutant exhibits reduced sleep in light independently of circadian rhythms

  • Prok2-induced sleep in light induces hypothalamic galn expression and requires galn

Summary

Light affects sleep and wake behaviors by providing an indirect cue that entrains circadian rhythms and also by inducing a direct and rapid regulation of behavior. While circadian entrainment by light is well characterized at the molecular level, mechanisms that underlie the direct effect of light on behavior are largely unknown. In zebrafish, a diurnal vertebrate, we found that both overexpression and mutation of the neuropeptide prokineticin 2 (Prok2) affect sleep and wake behaviors in a light-dependent but circadian-independent manner. In light, Prok2 overexpression increases sleep and induces expression of galanin (galn), a hypothalamic sleep-inducing peptide. We also found that light-dependent, Prok2-induced sedation requires prokineticin receptor 2 (prokr2) and is strongly suppressed in galn mutants. These results suggest that Prok2 antagonizes the direct wake-promoting effect of light in zebrafish, in part through the induction of galn expression in the hypothalamus.

Keywords

prokineticin 2
galanin
sleep
circadian rhythm
masking
zebrafish

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