Light-resetting impact on behavior and the central circadian clock in two vole species (genus: Lasiopodomys).

The behavioral circadian rhythms of subterranean rodents show intra- and interspecies diversity in terms of adaptation to dark underground environments, but the endogenous molecular mechanism of rhythm regulation in the suprachiasmatic nuclei (SCN) is stable to many species. In this study, we sought to determine the rhythms of behavior and central molecular regulatory mechanisms in the SCN of the subterranean Mandarin voles (Lasiopodomys mandarinus) compared with a related aboveground species, Brandt's voles (Lasiopodomys brandtii). Both species were reared under a 12 L:12 D cycle or in continuous darkness for 4 weeks. The pattern of wheel-running activity was similar in both species and had a periodicity of almost 24 h regardless of rearing conditions. However, the intensity of daily activity in Brandt's voles decreased markedly in darkness, while there was no significant difference in activity intensity in mandarin voles under different light regimes. In both vole species, all tested genes in the SCN showed significant time-dependent expression regardless of rearing conditions, and the expression levels of most genes did not differ significantly between different species and conditions. However, the peak phase shift in gene expression differed between the two species. In conclusion, behavioral patterns in mandarin and Brandt's voles were regulated by a stable molecular endogenous biological clock. The observed differences in activity intensity and phase shift suggest that different mechanisms regulate circadian rhythms in different living environments.