Fig. 3.
The effect of the duper mutation to shorten the free-running period does not underlie the phase-shifting phenotype. (A) Mean (± SEM) free-running period of duper hamsters consuming tap water (H2O) (blue, n = 5) or 25% D2O adulterated water (black, n = 5). D2O significantly lengthened the free-running period (t4 = 3.911, ****P < 0.0001). (B) Phase angle of entrainment estimated as time difference in hours between activity onset and lights off in duper hamsters consuming tap water (blue, n = 6) and D2O adulterated water (black, n = 6). Heavy water significantly shortened the phase angle of entrainment (F2,15 = 3.736, *P < 0.05). Upon reinstitution of pure water (post-D2O, cyan, n = 6), phase angle reverted to pre-D2O values (F2,15 = 2.963, P > 0.05). (C and D) Representative actograms plotted modulo τDD of a duper hamster when consuming tap water (C) and D2O adulterated water (D) while maintained in DD. The asterisk indicates 15’ light pulse at CT17.5. Lines fit to activity onsets were used to estimate the free-running period and calculate the phase shift that resulted from the light pulse. (E) Phase-shift amplitude (mean ± SEM, in circadian hours) in response to a 15’ light pulse presented at CT17.5 in duper hamsters consuming tap water (H2O, blue bar, n = 5) or water adulterated with D2O (gray bar, n = 5). (F) Latency to re-entrain to 8-h phase advance of the 14L:10D cycle in duper hamsters before (blue bar, n = 6), during (black bar, n = 6), or after (cyan bar, n = 6) consumption of drinking water adulterated with D2O. Although heavy water slowed the circadian clock of duper hamsters, it did not alter either the amplitude of phase shifts in response to light pulses in the mid subjective night or the rate of re-entrainment after an 8-h shift of the 14L:10D cycle.