Efeito ansiolítico do ondansetron, antagonista dos receptores 5-HT3, injetado na amídala de camundongos submetidos à exposição e reexposição no labirinto em cruz elevado

Abstract

Against of stimuli that are dangerous, animals manifest defense reactions that cause fear and anxiety. These stimuli activate the serotonergic system, which sends projections to structures involved in defense mechanisms such as the septum, hypothalamus, hippocampus, amygdala and periaqueductal gray modulates the behavioral changes that can be characterized as anxiety. Studies have shown that 5-HT3 receptors are part of this modulation. The elevated plus maze (EPM) is a widely used animal model to evaluate the anxiolytic activity of drugs. Currently, it is known that the retest in rodents (rats and mice) increases the avoidance of it, this phenomenon, which refers to "a display of tolerance" (OTT, One Trial Tolerance). The amygdala is a prosencephalic structures that have significant amount of serotonin (5-HT) in this way, recent results from our laboratory have shown that microinjections of ondansetron antagonist 5-HT3 receptors in the amygdala of mice produced anxiolytic-like effect evaluated in LCE. The aim of this study was to evaluate the involvement of receptors 5-HT3 receptors in the amygdala of mice prior experience the elevated plus-maze (EPM). Conventional measures of anxiety (% of entry and time spent in open arms), locomotor activity (frequency in closed arms) and ethological measures related to risk assessment were recorded. The present study demonstrated that intra-amygdala of ondansetron, antagonist of 5-HT3 receptors, produced anxiolytic-like effects in naive mice and mice prior experience the LCE. The injection of ondansetron in only one of the exhibits produced anxiolytic-like effect, which leads us to conclude that the drug produced no change in memory. Both the Trial 1 and in Trial 2, none treatments affected locomotor activity. So while the amygdala is involved in the neurobiology of the defense reactions such as anxiety response, as it refers to the phenomenon it seems OTT not to participate.