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Phasic and tonic serotonin modulate alarm reactions and post‐exposure behavior in zebrafish
Author(s) -
LimaMaximino Monica,
Pyterson Maryana Pereira,
Carmo Silva Rhayra Xavier,
Gomes Gabriela Cristini Vidal,
Rocha Sueslene Prado,
Herculano Anderson Manoel,
Rosemberg Denis Broock,
Maximino Caio
Publication year - 2020
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1111/jnc.14978
Subject(s) - serotonergic , tonic (physiology) , serotonin , freezing behavior , psychology , monoamine neurotransmitter , neuroscience , stimulation , zebrafish , endocrinology , neurotransmitter , arousal , medicine , chemistry , fear conditioning , amygdala , receptor , central nervous system , biochemistry , gene
Current theories on the role of serotonin (5‐HT) in vertebrate defensive behavior suggest that this monoamine increases anxiety but decreases fear, by acting at different levels of the neuroaxis. This paradoxical, dual role of 5‐HT suggests that a serotonergic tone inhibits fear responses, while an acute increase in 5‐HT would produce anxiety‐like behavior. However, so far no evidence for a serotonergic tone has been found. Using zebrafish alarm responses, we investigate the participation of phasic and tonic 5‐HT levels in fear‐like behavior, as well as in behavior after stimulation. Conspecific alarm substance (CAS) increased bottom‐dwelling and erratic swimming, and animals transferred to a novel environment after CAS exposure (post‐exposure behavior) showed increased bottom‐dwelling and freezing. Clonazepam blocked CAS effects during and after exposure. Acute fluoxetine dose‐dependently decreased fear‐like behavior, but increased post‐exposure freezing. Metergoline had no effect on fear‐like behavior, but blocked the effects of CAS on post‐exposure behavior; similar effects were observed with para ‐chlorophenylalanine. Finally, CAS was shown to decrease the activity of monoamine oxidase in the zebrafish brain after exposure. These results suggest that phasic and tonic serotonin encode an aversive expectation value, switching behavior toward cautious exploration/risk assessment/anxiety when the aversive stimulus is no longer present.