Efeito de ligantes do receptor da nociceptina/orfanina FQ no comportamento agressivo de camundongos machos

Abstract

INTRODUCTION: Several species including humans display aggressive behavior. However, violence and impulsivity related to aggressiveness represent a social problem. Indeed, aggressive behavior can be considered symptoms of many psychiatric disorders. Some of the brain areas involved in aggression include amygdala, hypothalamus, and prefrontal cortex. Aggressiveness is modulated by different neurotransmitters, such as serotonin, dopamine, noradrenaline and GABA. These systems represent the therapeutic targets available to treat aggressiveness. The nociceptin/orphanin FQ (N/OFQ) is a heptadecapeptide acting as endogenous ligand of NOP receptor. Clinical and preclinical findings suggest the involvement of N/OFQ – NOP receptor system with psychiatric disorders, including those related to aggressiveness. AIM: This study investigated the effects of standard drugs as well as NOP receptor ligands on aggressiveness in mice submitted to the resident-intruder test. METHODS: Male Swiss mice were used to develop this study. Valproate 300 mg/kg, Lithium 50 mg/kg, Carbamazepine 20 mg/kg, and Diazepam 1 mg/kg were used as standard drugs. The NOP ligands Ro 65-6570 (0.01 – 1 mg/kg), full agonist, AT-090 (0,01 – 0,1 mg/kg), partial agonist, and SB-612111 (1 – 10 mg/kg), antagonist, were used. In the resident-intruder test, male mice were housed individually for 7 days (residents) before the experiment. The aggressiveness of each resident mouse was tested twice, at 8th and 11th days, by inserting an intruder mouse in the resident cage for 10 min. Day 8 of experiment, the basal aggressiveness of resident mice was recorded without pharmacological treatment; Day 11 of experiment, the same mouse was re-tested after being treated. The open field was used to evaluated the spontaneous locomotor activity . RESULTS: Valproate, Lithium, and Carbamazepine reduced the aggressive behavior of resident mice, while Diazepam did not affect the agressiveness. Ro 65-6570 (at all doses) and AT-090 (at the highest dose), increased aggressiveness. The partial agonist, AT-090, at lowest doses, slightly reduced aggressive behavior. The treatment with SB-61211 did not modified the aggressive behavior of mice. None of the treatments affected the locomotor activity. CONCLUSION: Standard drugs used in therapy for psychiatric disorders were effective on aggressiveness control in the resident mice. In contrast, the activation of NOP receptor tends to increase the aggressive behavior, while the blockade of this signal did not modify this behavior. Ultimately, these data suggest that NOP agonists could increase aggressive behavior as an adverse event.