Frequency Analysis of Periods of Spontaneous Biological Rhythm in Mice under Different Light-dark Cycle

Objective To make clear whether circaseptan and circasemiseptan rhythms exist as endogenous rhythms, and to investigate whether organisms have a 10 d rhythm. Method Mice were used as the animal model. Multi-frequency biological rhythm of mice locomotor activity under the different light (L)-dark (D) cycle conditions were analyzed. Result The results showed that under 10 h(L)/10 h(D) cycle, mice (n=6) had an overt circadian (τ=20 h) and circasemidian (τ=10 h) rhythms(P0.001), and a slight circaseptan and circasemiseptan rhythm with periods;under 12 h(L)/12 h(D) cycle, circadian (τ=24 h) and circasemidian (τ=12 h) rhythm were observed definitely in mice(P0.001), however, circaseptan and circasemiseptan rhythm were not found. When living under 14 h(L)/14 h(D) cycle, mice presented circadian (τ=28 h) and circasemidian (τ=14 h) rhythms obviously (P0.001), but circaseptan and circasemiseptan rhythms were not obvious. Anyhow, no 10 d rhythm was found in the mice living under any different L-D cycle. Conclusion Multi-frequency biological rhythms do exist in mice and they are affected by different L-D cycle.