Neuropeptidergic Signaling Partitions Arousal Behaviors in Zebrafish

Abstract

Animals modulate their arousal state to ensure that their sensory responsiveness and locomotor activity match environmental demands. Neuropeptides can regulate arousal, but studies of their roles in vertebrates have been constrained by the vast array of neuropeptides and their pleiotropic effects. To overcome these limitations, we systematically dissected the neuropeptidergic modulation of arousal in larval zebrafish. We quantified spontaneous locomotor activity and responsiveness to sensory stimuli after genetically induced expression of seven evolutionarily conserved neuropeptides, including adenylate cyclase activating polypeptide 1b (adcyap1b), cocaine-related and amphetamine-related transcript (cart), cholecystokinin (cck), calcitonin gene-related peptide (cgrp), galanin, hypocretin, and nociceptin. Our study reveals that arousal behaviors are dissociable: neuropeptide expression uncoupled spontaneous activity from sensory responsiveness, and uncovered modality-specific effects upon sensory responsiveness. Principal components analysis and phenotypic clustering revealed both shared and divergent features of neuropeptidergic functions: hypocretin and cgrp stimulated spontaneous locomotor activity, whereas galanin and nociceptin attenuated these behaviors. In contrast, cart and adcyap1b enhanced sensory responsiveness yet had minimal impacts on spontaneous activity, and cck expression induced the opposite effects. Furthermore, hypocretin and nociceptin induced modality-specific differences in responsiveness to changes in illumination. Our study provides the first systematic and high-throughput analysis of neuropeptidergic modulation of arousal, demonstrates that arousal can be partitioned into independent behavioral components, and reveals novel and conserved functions of neuropeptides in regulating arousal.

Calcitonin Gene-Related Peptide Neurons Mediate Sleep-Specific Circadian Output in Drosophila

“…While not previously addressed experimentally, the intimate relationship between stress, anxiety, and sleep [5] suggest that CGRP might regulate sleep. Potentially relevant to this possibility is the recent observation that acute activation of CGRP signaling in zebrafish larvae increases spontaneous locomotor activity and decreases quiescence [33]. Our analysis of gain-of-function and loss-of-function mutant flies establishes that DH31, the Drosophila homologue of CGRP, is a negative regulator of sleep maintenance that awakens the animal in anticipation of dawn.…”

“…DH31 and its receptor (DH31-R1) are homologous to vertebrate CALCITONIN GENE RELATED PEPTIDE (CGRP) and its receptor (CLR) [29–32], which have been shown to increase locomotion in zebrafish [33], but whose role in sleep has not been investigated. By analysis of DH31 loss-of-function and gain-of-function mutations we demonstrate that DH31 is a wake-promoting signal that acts late at night to arouse flies in anticipation of dawn.…”

Effects of embryonic ethanol exposure at low doses on neuronal development, voluntary ethanol consumption and related behaviors in larval and adult zebrafish: Role of hypothalamic orexigenic peptides

“…Whereas there are no reports in zebrafish examining the direct effects of these peptides on ethanol consumption, there is evidence in teleosts that central injection of GAL or OX can significantly increase the intake of food [39–41]. Also, central injection of OX in zebrafish [40] and the overexpression of OX in mutant fish [42, 43] are shown to increase locomotor behavior, while the overexpression of GAL in mutant mice is associated with a decrease in locomotor acitivity [43]. These studies hint at the possibility that these orexigenic peptides have a role in mediating ethanol consumption and related behaviors in zebrafish, similar to their functions in rodents, suggesting that this vertebrate species may be a good model for investigating using genetic techniques the precise mechanisms underlying these behavioral phenomena.…”

Motivated state control in larval zebrafish: behavioral paradigms and anatomical substrates

“…Experiments using controlled expression of neuropeptides in larvae further suggest that motivational states selectively regulate sensory systems. For instance, after increasing hypocretin levels, larvae show increased responsiveness to dark-flash visual stimuli, but no change in responses to acoustic or thermal stimuli (Woods et al, 2014). Changes in responsiveness to sensory stimuli do not necessarily reflect altered sensitivity of the sensory apparatus.…”