Celio Estanislau

Effects of under-and overcrowding on exploratory behavior in the elevated plus-maze

The present work investigated whether the number of rats housed in a cage affects exploration of an elevated plus-maze. Male Wistar-derived rats were kept 1, 2, 3, 4, 6, 8, 12, 16, or 24 to same size cages either for 1 or 14 days and tested in the elevated plus-maze. Rats kept 6 to a cage were arbitrarily considered controls because this is the housing condition adopted in many laboratories, ours included. In comparison to controls, 1-day housed rats kept 1, 2, 16, and 24 to a cage decreased the percentage of entries into the open arms. Similar decreases were also found in the time spent in the open arms, the only exception being the group with rats kept 16 to a cage which failed to show significant differences from the control group. Fourteen-day housed rats kept 1, 2, 16, or 24 to a cage decreased the percentage of entries and time spent in the open arms. We found plus-maze exploration to be similar in groups in which rats were kept from 4 to 12 to a cage. The present data indicate that anxiogenic effects resulting from under- and overcrowding should be taken into consideration in behavioral studies.

Individual differences in the elevated plus-maze and the forced swim test

The elevated plus-maze is an apparatus composed of enclosed and open (elevated) arms and time spent in the open arms by a rat can be increased/decreased by anxiolytic/anxiogenic agents. In the forced swim test, floating behavior is used as an index of behavioral despair and can be decreased by antidepressant agents. As the comorbidity between anxiety and depression is a remarkable issue in human behavioral disorders, a possible relationship between the behaviors seen in the cited tests is of great relevance. In the present study, fifty-four male rats (Rattus norvegicus) were submitted to a plus-maze session and to a 2-day forced swim protocol. According to their time in the open arms, they were divided into three groups: Low Open, Medium Open and High Open. Some plus-maze measures were found to be coherent with time in the open arms and are suggested to also be reliable anxiety indexes. In the forced swim test, the Low Open group showed decreases in floating duration from forced swim Session 1 to Session 2, an alteration opposite to that observed in the other groups (particularly, the Medium Open group). The Low Open group also showed increases in floating latency, again in sharp contrast with the alteration found in the other groups. Accordingly, positive and negative correlation were found between time in the open arms and floating duration and latency, respectively. Results are compared to previous studies and mediation of the effect by reactivity to aversive stimulation or alterations induced by open arm exposure is discussed.

Bosentan, a mixed endothelin receptor antagonist, induces antidepressant-like activity in mice

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.

Efeitos comportamentais e imunológicos da fluoxetina em ratos submetidos ao nado forçado

Evidencias sugerem que a depressao envolve alteracoes imunologicas. No presente trabalho, os efeitos comportamentais e imunomoduladores de um antidepressivo, a fluoxetina, sao avaliados num modelo animal de depressao, o nado forcado. Nesse modelo, o comportamento de flutuar e usado como indice de desespero comportamental. Ratos foram tratados por 12 dias com fluoxetina ( 10mg/kg ) tres vezes ao dia ou com salina; e, nos mesmos dias, foram submetidos a sessoes de nado forcado. Adicionalmente, a resposta imune humoral a uma imunoestimulacao foi avaliada. Os animais tratados com fluoxetina apresentaram menor producao total de anticorpos e queda de massa corporal, alem d e passarem mais tempo flutua ndo. Os resultados sugerem que o desespero comportamental e a producao de anticorpos sao simultaneamente atenuados pela fluoxetina.

Evaluation of the Humoral Immune Response of Wistar Rats Submitted to Forced Swimming and Treated with Fluoxetine

The term stress was introduced into the biomedical field by Hans Selye (1936) in reference to a General Adaptation Syndrome which would consist of all non-specific systemic reactions that occur during an intense and chronic exposure to a stressor (e.g., pressure at work and poor diet). This syndrome would be different from the specific adaptive reactions (such as muscle hypertrophy caused by exercise performed on a regular basis) and immune responses (Selye, 1936).

MODERATE INTENSITY PHYSICAL EXERCISE: PSYCHONEUROIMMUNOLOGICAL ASPECTS

Rev Bras Med Esporte – Vol. 24, No 5 – Set/Out, 2018 ABSTRACT The literature presents several instances of interaction between the nervous system (NS) and the immune system (IS). These interactions are promoted by several molecules, such as cytokines and hormones, with modulating action for both the NS and IS. In this sense, the two systems may influence each other: changes in behavior may be accompanied by alterations in the IS (e.g., immunosuppression) and immunological disorders, such as infections, may modulate behavior (e.g., anxiety and depression). Considering that chronic stress, in addition to affecting behavior, also modulates the IS and that there is evidence that moderate intensity physical exercise (PE) protects physical and mental health, the objective of this review is to explore the influence of moderate-intensity PE on behavior and immunity. Level of Evidence V; Expert opinion.

Recognition of a response to potential threat: Evidence for a facial expression of anxiety?

Anxiety is widely known to compose symptoms of a considerable number of psychiatric disorders. A previous report suggested a facial expression for anxiety. To replicate and expand on this subject, we tested the accuracy with which observers would match an apparent risk-assessment facial behavior with potentially threatening fictitious scenarios. In an attempt to portray different Brazilian ethnic groups, we first selected as participants three actors and four actresses who had distinct physical characteristics. These participants posed facial expressions in response to the narration of 21 emotional scenarios. Poses were videotaped, from which pictures were extracted to compose answer choices for a 21-item task. Second, 100 observers answered those multiple-choice items by indicating the facial expression that best matched each scenario. We analyzed both the general accuracy for matching scenarios with emotional faces, and the accuracy for matching potential threat scenarios with risk-assessment expressions in comparison with other emotional faces. Results indicated that potential threat scenarios produced distinct facial expressions, characterized by typical environmental scanning facial behavior (related to risk assessment), which were distinguished from other known universal facial expressions of emotions. Our findings suggest that this facial behavior may be related to anxiety in humans. Further studies are needed to confirm the cross-cultural nature of this putative anxiety behavior.