3.2 Chronic caffeine treatment induced circasemidian (~12h), circadian, and longer activity rhythms in CryDKO.
We administered 0.05% caffeine to CryDKO (n=16; Table 1) under LD. After 7 days, the mice were moved to DD. In DD, CryDKO exhibited behavioral rhythms that changed over time (Table 1). Of the 16 CryDKO, 15 exhibited circasemidian (8.75-17.16 h period) activity rhythms. 7 animals demonstrated circadian (20.75-26.66 h period) activity rhythms. For example, CryDKO#13 displayed an altered activity period from 13.75 h (7d) to 23.83 h (3d) and 15.16 h (6d) (Figure 2a). CryDKO#09 displayed an altered activity period from 17.08 h (7d) to 14.33 h (4d) and 12.00 h (5d) (Figure 2b). CryDKO#14 displayed an altered activity period from 15.16 h (6d) to 20.75 h (6d) and 13.08 h (3d) (Figure 2c). 7 animals demonstrated much longer activity periods (28.16-39.41 h). For example, CryDKO#07 displayed an altered activity period from 29.25 h (5d) to 13.33 h (2d) and 30.00 h (10d) (Figure 3a). CryDKO#10 displayed an altered activity period from 28.33 h (5d) to 17.16 h (3d) and 30.91 h (5d) (Figure 3b). One animal did not demonstrate circasemidian or circadian rhythms for 37 days. The average amount of spontaneous caffeine intake was 2.8±0.19 mg/day/animal. After caffeine withdrawal, all the CryDKO became arrhythmic.