Naloxone Prolongs Abdominal Constriction Writhing-Like Behavior in a Zebrafish-Based Pain Model

Abstract

The ability to detect noxious stimuli is essential to survival. However, pathological pain is maladaptive and severely debilitating. Endogenous and exogenous opioids modulate pain responses via opioid receptors, reducing pain sensibility. Due to the high genetic and physiological similarities to rodents and humans, the zebrafish is a valuable tool to assess pain responses and the underlying mechanisms involved in nociception. Although morphine attenuates pain-like responses of zebrafish, there are no data showing if the antagonism of opioid receptors prolongs pain duration in the absence of an exogenous opioid. Here, we investigated whether a common opioid antagonist naloxone affects the abdominal constriction writhing-like response, recently characterized as a zebrafish-based pain behavior. Animals were injected intraperitoneally with acetic acid (5.0%), naloxone (1.25 mg/kg; 2.5 mg/kg; 5.0 mg/kg) or acetic acid with naloxone to investigate the changes in their body curvature for 1 h. Acetic acid elicited a robust pain-like response in zebrafish, as assessed by aberrant abdominal body curvature, while no effects were observed following PBS injection. Although naloxone alone did not alter the frequency and duration of this behavior, it dose-dependently prolonged acetic acid-induced abdominal curvature response. Besides reinforcing the use of the abdominal writhing-like phenotype as a behavioral endpoint to measure acute pain responses in zebrafish models, our novel data suggest a putative role of endogenous opioids in modulating the recovery from pain stimulation in zebrafish. © 2019 Elsevier B.V.We recognize the financial support and fellowships from Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq), Fundação de Amparo à Pesquisa do Estado do Rio Grande do Sul (FAPERGS), and Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) . F.V.C. was recipient of CAPES fellowship. J.C. and F.V.S. receive the CNPq fellowship. D.B.R. is a recipient of CNPq research productivity grant ( 305051/2018-0 ) and his work is also supported by the PROEX/CAPES (process number 23038.005848/2018-31) and PRONEM/FAPERGS (process number 16/2551-0000248-7) fellowship grants. A.V.K. is the Chair of the International Zebrafish Neuroscience Research Consortium (ZNRC). His research is supported by the Russian Science Foundation (RSF) grant 19-15-00053. All authors contributed to the preparation of the manuscript and approved its final version. The funders had no influence on the study design, collection, analysis, and interpretation of data, as well as on writing and submission of this manuscript