[Background and purpose] The Aggressive Response Meter (ARM) can be used to evaluate the efficacy of drugs that are effective in treating aggressive biting behavior of this isolated-reared mouse (Igarashi et al., Brain Res., 2021). However, the pathology caused by isolation-rearing stress is complex, and it was not clear what symptoms this aggression was associated with. In this study, we conducted multiple behavioral tests on isolation-reared mice and investigated the correlation of each experimental parameter for each individual.
[Method] Male and female ddY strain mice were individually bred from 3 weeks after birth, and biting behavior was measured at 10 weeks of age. In addition, open field test (OFT), a resident-intruder (R-I) test, and elevated plus maze (EPM) were conducted.
[Results] When the correlation coefficient of Pearson was examined for the bite strength measured by ARM and the number of aggression behaviors in the R-I test for isolated male mice, it showed a negative value (r = -0.40, p = 0.26), no aggressive behavior was observed in the R-I test in female mice. In addition, when the relationship between biting intensity and time in central zone was investigated in OFT, a weak positive correlation was shown in male mice (r = 0.23, p = 0.51), and a positive correlation was shown in female mice (r = 0.63, p = 0.049). Examination of biting intensity and open arm residence time in EPM showed a negative correlation in male mice (r = -0.61, p = 0.06) and a weak positive correlation in female mice (r = 0.20, p = 0.58).
[Discussion] The bite strength measured by ARM is considered to reflect some pathological aggression (Kuchiiwa and Kuchiiwa, J. Neurosci. Methods, 2014). From the above results, it is considered that the aggressive biting behavior measured by ARM indicates some features of mental symptoms in each sex.