Opioid neurotransmission modulates defensive behavior and fear-induced antinociception in dangerous environments

• Autor(a) principal: Coimbra, Norberto Cysne
• Data de Publicação: 2017
• Outros Autores: Soares, Bruno Lobão, Calvo, Fabrício, Almada, Rafael Carvalho, Freitas, Renato Leonardo, Paschoalin-Maurin, Tatiana, Anjos-Garcia, Tayllon dos, Elias-Filho, Daoud Hibrahim, Ubiali, Walter Adriano, Tracey, Irene
• Tipo de documento: Artigo
• Idioma: eng
• Título da fonte: Repositório Institucional da UFRN
• Texto Completo: https://repositorio.ufrn.br/handle/123456789/49633; https://doi.org/10.1016/j.neuroscience.2017.04.032
• topic: innate fear; conditioned fear/anticipatory anxiety; panic attacks; endogenous opioid peptide-mediated neural system; prey-versus-rattlesnake pit viper paradigm; instinctive fear-induced antinociception

The effects of endogenous opioid peptide antagonists on panic-related responses are controversial. Using elevated mazes and a prey-versus-predator paradigm, we investigated the involvement of the endogenous opioid peptide-mediated system in the modulation of anxiety- and panic attack-induced responses and innate fear-induced antinociception in the present work. Wistar rats were intraperitoneally pretreated with either physiological saline or naloxone at different doses and were subjected to either the elevated plus- or T-maze test or confronted by Crotalus durissus terrificus. The defensive behaviors of the rats were recorded in the presence of the predator and at 24 h after the confrontation, when the animals were placed in the experimental enclosure without the rattlesnake. The peripheral non-specific blockade of opioid receptors had a clear anxiolytic-like effect on the rats subjected to the elevated plus-maze but not on those subjected to the elevated T-maze; however, a clear panicolytic-like effect was observed, i.e., the defensive behaviors decreased, and the prey-versus-predator interaction responses evoked by the presence of the rattlesnakes increased. A similar effect was noted when the rats were exposed to the experimental context in the absence of the venomous snake. After completing all tests, the naloxone-treated groups exhibited less anxiety/fear-induced antinociception than the control group, as measured by the tail-flick test. These findings demonstrate the anxiolytic and panicolytic-like effects of opioid receptor blockade. In addition, the fearlessness behavior displayed by preys treated with naloxone at higher doses enhanced the defensive behavioral responses of venomous snakes.