RESUMO
Rodent self-grooming is a stereotyped behavior that can rise due to stressors such as novelty. In the present study, the occurrence of a rebound effect was investigated by means of manipulation of contextual novelty and of the possibility of self-grooming (with an Elizabethan collar which blocked head-body contact). Fourty-six male rats were submitted to an experiment latter replicated with 43 females. Half of the animals were submitted to habituation sessions (30 min) to the test box in three days. The other half was similarly handled but habituated to small cages. On the fourth day, rats from both conditions were assigned to Elizabethan or sham collar groups. Each animal was observed for 15 min with its respective collar and for other 15 min with no collars. Increased locomotion was observed in the rats not habituated to the test box. Such habituation did not affect any grooming parameter. On the other hand, the animals wearing Elizabethan collars during the first half of the test, as compared to those which wore sham collars, showed increased self-grooming during the second half of the test (i.e., with no collars). Females showed pretty similar results. Present results, thus, evidence a rebound effect in self-grooming.
Assuntos
Asseio Animal , Animais , Feminino , Masculino , RatosRESUMO
Endothelins are peptides described initially as potent vasoactive mediators. Recently, studies reported that endothelins can modulate the production and release of cytokines by immune cells. In turn, cytokines are involved in depression disorders and also in the effectiveness of some antidepressants. Therefore, we investigated the effects of treating mice with bosentan, a mixed endothelin receptor antagonist, in widely used models for assessing antidepressant activity of compounds, the forced swimming (FST) and the tail suspension tests (TST). Moreover, the influence of bosentan treatment on circulating IL-6 levels was also addressed after FST. The results show that bosentan treatment induced a bell shaped dose-dependent antidepressant-like effect with increase in circulating IL-6 levels in animals exposed to FST. Bosentan also presented antidepressant-like effect in TST. Similar results were obtained with nortriptyline treatment in the FST and TST. Possible anxiogenic effect of bosentan was excluded using the elevated plus maze test. Therefore, this is the first study to demonstrate the antidepressant-like activity of bosentan in mice, unveiling a previous unrecognized role of endothelin in depression and its possible relation with increased circulating IL-6 levels.