Imunorreatividade de c-Fos em áreas telencefálicas do lagarto Tropidurus hispidus (SPIX, 1825) submetido a um estímulo aversivo

Abstract

Introduction: Fear is characterized as the physiology and behavioral response face to a stimulus that act as a danger to the individual. In animals, one of the fear-like behavior most observed is freezing. In order to know which brain areas may be modulating this and other behaviors, evaluating the immunoreactivity for c-Fos protein is a model already consolidated in the literature. In the reptile’s group, there is a paucity of studies that address the neurobiology of fear, However, research in this area is needed for the compression of the neurocircuitry involved in the modulation of this behavior. Therefore, present study aimed to evaluate the immunoreactivity for c-Fos in the telencephalic areas of these animals after being exposed to the aforementioned aversive stimulus and how these areas might be related to fear-like behavior. Methodology: All protocols were duly approved by the Animal Research Ethics Committee under number 26/2016. Eighteen animals were divided into 3 groups: Control Group (CTR) - animals that did not pass the behavioral test, Neutral Stimulus Group (EN) - animals that were exposed to an empty cage, and Aversive Stimulus Group (EA) - animals that were exposed to a cage containing a domestic cat inside. Após 5 dias de ambientação ao laboratório, os animais, foram expostos a um campo aberto por 10 minutos (Fase de habituação) e logo em seguida por 10 minutos a seu respectivo estímulo (Fase de exposição). Parâmetros comportamentais (distância percorrida, tempo de imobilidade, latência para o primeiro deslocamento, latência para o primeiro movimento e número de quadrantes visitados) foram coletados e 90 min após um dos respectivos estímulos, os animais foram perfundidos e os cérebro removidos para processamento da imunorreatividade para c-Fos. Results: Behavioral data showed that the EA group, when compared to the EN group in the exposure, had: shorter distance walked, longer freezing time and longer latency to initiate a movement, a difference that was not observed in the latency to initiate a movement. As for cell count data for c-Fos protein labeling, the EA group showed an increase in the number of c-Fos positive cells when compared to EN or CTR in the following areas: Medial Cortex, Dorsomedial Cortex, Lateral Cortex, Amygdala, Striate, Septum, and Posterior Dorsal Ventricular Region. Furthermore, it was possible to observe a negative correlation between the number of activated cells in the Amygdala and Septum, with the distance covered. Conclusion: The behavioral and cell count results suggest that there is an interaction between the aforementioned areas and the fear behaviors of the lizard Tropidurus hispidus, when exposed to an aversive stimulus.