Differential susceptibility of BALB/c, C57BL/6N, and CF1 mice to photoperiod changes

Objective:Circadian disturbances common to modern lifestyles have been associated with mood disorders. Animal models that mimic such rhythm disturbances are useful in translational research to explore factors contributing to depressive disorders. This study aimed to verify the susceptibility of BALB/c, C57BL/6N, and CF1 mice to photoperiod changes.Methods:Thermochron iButtons implanted in the mouse abdomen were used to characterize temperature rhythms. Mice were maintained under a 12:12 h light-dark (LD) cycle for 15 days, followed by a 10:10 h LD cycle for 10 days. Cosinor analysis, Rayleigh z test, periodograms, and Fourier analysis were used to analyze rhythm parameters. Paired Student's t test was used to compare temperature amplitude, period, and power of the first harmonic between normal and shortened cycles.Results:The shortened LD cycle significantly changed temperature acrophases and rhythm amplitude in all mouse strains, but only BALB/c showed altered period.Conclusion:These findings suggest that BALB/c, the preferred strain for stress-induced models of depression, should also be favored for exploring the relationship between circadian rhythms and mood. Temperature rhythm proved to be a useful parameter for characterizing rhythm disruption in mice. Although disruption of temperature rhythm has been successfully documented in untethered mice, an evaluation of desynchronization of other rhythms is warranted.

Desenvolvimento da versão breve da Escala de Ritmo Social / Development of brief version of the Social Rhythm Metric

OBJETIVO: O objetivo deste trabalho é o estabelecimento de uma versão abreviada da Escala de Ritmo Social, com vistas à aplicação em pesquisa. MÉTODOS: Tomando como padrão-ouro a Escala de Ritmo Social de 17 itens, estabelecidas três versões breves a partir de três critérios diferentes. Comparados escores de regularidade e quantidade de atividades desenvolvidas em um período de uma semana de 167 sujeitos saudáveis, 25 portadores de epilepsia mioclônica juvenil e 16 portadores de transtorno depressivo. RESULTADOS: A versão breve de seis itens mostrou melhor concordância com relação ao padrão-ouro k = 0,51; p < 0,001. A análise bivariada demonstrou significativa correlação entre a versão breve-6 e o padrão-ouro: (r = 0,87; p < 0,001). Houve correlação com idade na versão breve-6 (r = 0,2; p < 0,001), ainda mais significativa do que no padrão-ouro (r = 0,2; P < 0,01). Na análise ANOVA, o grupo saudável apresentou escores mais altos de regularidade em ambas as escalas. Com relação à quantidade de atividades, o grupo saudável assemelhou-se ao dos portadores de epilepsia e o dos portadores de depressão apresentou médias mais baixas. CONCLUSÃO: A simplificação da escala diminui a porcentagem de itens não preenchidos e custo em material impresso e facilita a padronização. O processo envolveu cuidadosa análise da adequação do instrumento à cultura-alvo.

OBJECTIVE: The objective of this work was to establish a brief version of the Social Rhythm Metric, aimed at applying it in research. METHODS: Taking the 17-item Social Rhythm Metric as the gold standard, three brief versions were created based on three different criteria. compared the scores of the regularity and quantity of activities carried out in a week for 167 healthy subjects and 25 individuals with juvenile myoclonic epilepy and 16 with depressive disturbance. RESULTS: The brief version of 6 items showed better concordance in relation to the gold standard; k = 0.51, p < 0.001. Bivariate analysis demonstrated a significant correlation between the brief version 6 and the gold standard (r = 0.87; p < 0.001). There was a correlation with age in the brief 6 version (r = 0.2; p < 0.001), even more significant than in the gold standard (r = 0.2; P < 0.01). ANOVA showed higher scores for regularity in the healthy using both scales. However, in relation to the quantity of activities, the healthy group resembled the epilepsy group, and the individuals with depression showed lower means. CONCLUSION: The simplification of the Social Rhythm Metric decreased the percenta-ge of items not filled in and the cost of printed matter and facilitate the standardization. The process involved a careful analysis of suitability of the instrument for the target culture.