Evaluation of behavioral responses to restraint stress in the house mouse (Mus musculus musculus) of wild origin

Stress is a fundamental concept for many areas of animal research. In laboratory rodents, exposure to various stressors results in immediate and postponed behavioral changes that can be measured with standard tests. Less is known about how wild rodents that have not undergone domestication respond to stressors in laboratory settings. This study was aimed at evaluating behavioral responses to restraint stress in male and female wild-derived house mice (Mus musculus musculus). One week after the end of three daily restraint sessions, alterations in mouse behavior were assessed in two tests. In the open field test, stressed mice (n = 23) entered the unprotected central zone less frequently (P < 0.05) and showed increased duration of self-grooming (P < 0.05) compared to controls (n = 23), indicating elevated anxiety. In the forced swim test, most mice (44 out of 46) displayed episodes of behavioral despair, but the influence of stress was insignificant. To characterize baseline performance of wild-derived mice, their behavior was compared to that of a laboratory strain. As compared to C57BL/6 males (n = 10), M. m. musculus males (n = 14) showed significantly greater exploratory activity in the open field and longer latency of the first immobility episode in the forced swim test (P < 0.001). Overall, these findings confirm ecological validity of the widely used animal model of restraint stress and may serve as a basis for future studies.