Figure 3.

Reentrainment of Per1 expression in the SCN to 6 h phase delay in the light cycle. a, Steady-state phases of the Per1-luc rhythm. The phase of the 15 regions of the SCN are displayed as histograms with the position on the surface of the SCN indicated. For quantitative and statistical comparisons, the bold histogram represents the dorsomedial region, and the histogram surrounded by dashes indicates the ventrolateral histogram. Asterisks on the tops of histograms indicate regions that were statistically significantly different in phase from the dorsomedial region (Tukey's test; p < 0.05). The phase plane formed by the tops of the histograms is tipped upward in the top left corner, revealing that the dorsomedial region phase leads other regions. b, Phase plane on day 1 after 6 h delay in light schedule. The orientation of the plane reveals that the lateral region of the SCN has shifted more than the medial regions. c, By day 3 after the light schedule delay, the phase plane orientation is similar to the control orientation, indicating that the phase shift is essentially complete in all regions of the SCN. d, Circadian rhythms in Per1-luc expression in dorsomedial (filled circles) and ventrolateral (open circles) regions of the SCN before shift in light schedule (control). e, Per1-luc rhythms on day 1 after light cycle delay. f, Per1-luc rhythms on day 3. Controls are shown in dashed lines, dark dashes for dorsomedial region. In d-f, error bars indicate SE. ZT is time of light cycle just before recording; thus, ZT is for 6 h delayed light schedule in b and c.