[Chronosensitivity to absolute hypercapnia in various light regimens]

The studies of mice on the natural regimen of day and night alterations have revealed a daily rhythm of hypercapnia toxicity, with the maximum sensitivity observed at 6 a.m. and the minimum sensitivity at 6 p.m.-2 a.m. and 2 p.m.-6 p.m. The experiments on animals kept for 2 weeks-1 month on the constant light regimen have demonstrated the shift in sensitivity acrophase to 10 a.m.-4 p.m. and the prolongation of the daily period of increased sensitivity. With the animals' return to the natural regimen, a two-peak rhythm with the maximum sensitivity at 2 a.m. and 10 a.m.-2 p.m. and the minimum sensitivity at 22 p.m. and 6 a.m. was observed during the first 2 weeks-1 month. 2 months later the rhythm curve flattening was recorded, with the initial daily sensitivity rhythm to absolute hypercapnia recovering in 2 1/2 months.