Comparison of circadian rhythm parameters in wild-type and Per1−/− mice.

Cosine curves were fit to the multi-unit (MUA) neural activity data recorded from wild-type or Per1−/− SCN in the light-dark cycle (LD; 3 d) or in constant darkness (DD; 3 d) using periods ranging from 22 to 26-h by 0.1-h steps. For the best period, the mesor and amplitude were determined. Fifteen-min light pulses (100 lux) were administered at CT15 (3 h after activity onset). The relative MUA response during the light pulse was determined for each mouse by dividing the average relative MUA response (%) during the 15 min light pulse by the average MUA (%) during the 15 min before the light pulse. Then the mean relative MUA responses during the light pulse were averaged for each genotype. To determine the magnitudes of the phase shifts, one regression line was fit to the onset of activity or acrophase of the MUA rhythm for 3 d before the light pulse and the second line was fit to the 4 d following the light pulse (excluding the first cycle immediately after the pulse) and the phase shift was calculated that took into account the change in period that occurred with the light pulse. Data are the mean ± SD; n = 4 wild-type and n = 4 Per1−/− mice.#Student's t-test,##Welch's t-test,###Mann-Whitney U test.