Social defeat protocol and relevant biomarkers, implications for stress response physiology, drug abuse, mood disorders and individual stress vulnerability: a systematic review of the last decade / Protocolo de derrota social e biomarcadores relevantes, implicações para a fisiologia de resposta ao estresse, abuso de drogas, transtornos do humor e vulnerabilidade individual ao estresse: revisão sistemática de estudos na última década

Introduction: Social defeat (SD) in rats, which results from male intraspecific confrontations, is ethologically relevant and useful to understand stress effects on physiology and behavior. Methods: A systematic review of studies about biomarkers induced by the SD protocol and published from 2002 to 2013 was carried out in the electronic databases PubMed, Web of Knowledge and ScienceDirect. The search terms were: social defeat, rat, neurotrophins, neuroinflammatory markers, and transcriptional factors. Results: Classical and recently discovered biomarkers were found to be relevant in stress-induced states. Findings were summarized in accordance to the length of exposure to stress: single, repeated, intermittent and continuous SD. This review found that the brain-derived neurotrophic factor (BDNF) is a distinct marker of stress adaptation. Along with glucocorticoids and catecholamines, BDNF seems to be important in understanding stress physiology. Conclusion: The SD model provides a relevant tool to study stress response features, development of addictive behaviors, clinic depression and anxiety, as well as individual differences in vulnerability and resilience to stress. .

Introdução: A derrota social (social defeat, SD) entre ratos, resultado da confrontação intraespecífica entre machos, é etologicamente relevante e útil para o entendimento dos efeitos do estresse na fisiologia e no comportamento. Métodos: Foi realizada uma revisão sistemática de estudos sobre biomarcadores induzidos pelo protocolo de SD publicados entre 2002 e 2013, usando as bases de dados PubMed, Web of Knowledge e ScienceDirect. Os termos usados na busca foram: derrota social, neurotrofinas, marcadores neuroinflamatórios e fatores de transcrição. Resultados: Biomarcadores clássicos ou recentemente descobertos mostraram-se relevantes nos estados induzidos pelo estresse. Os achados foram resumidos de acordo com o tempo de exposição ao estresse: SD única, repetida, intermitente ou contínua. O fator neurotrófico derivado do cérebro se mostrou um marcador específico de adaptação ao estresse. Assim como glicocorticóides e catecolaminas, o BDNF parece ser importante para o entendimento da fisiologia do estresse. Conclusão: O modelo de SD oferece uma ferramenta importante para estudar características da resposta ao estresse, desenvolvimento de comportamentos aditivos, depressão clínica e ansiedade, bem como diferenças individuais de vulnerabilidade e resiliência ao estresse. .

Tryptophan diet reduces aggressive behavior in male mice

A tryptophan diet reduces aggressive behavior in different species, although some controversial findings have been reported. We studied 65 male mice divided into four groups according to increasing dosages of tryptophan (10, 20, 30, and 100 mg/kg) and a control group (vehicle). The first four groups ingested 10, 20, 30, and 100 mg/kg tryptophan together with cellulose vehicle and water by gavage before the behavioral tests that sought to record aggressive behavior. The control group received only the vehicle at the same time that the other groups received the tryptophan solutions. The results showed that low concentrations (10 and 20 mg/kg) of tryptophan decreased (p < .04) the frequency of attack bites and lateral threats (i.e., aggressive components; p < .02) after an encounter with a male intruder without altering locomotor activity. In conclusion, the low concentrations of tryptophan diminished aggressive behavior against a male intruder...