Figure 1.
The effect of light on SCN and adrenal gene expression and plasma hormone levels.
A: Relative density of Per1, Per2 and c-fos expression in the SCN following a light pulse (LP; 30 min at 350 lux) beginning at the indicated circadian time (CT) points compared to dark control (DC) mice. B: Relative expression of Per1 and Per2 in the adrenal following a LP compared to DC animals at several CT points throughout the subjective day and subjective night. C: Plasma levels of corticosterone (left) and ACTH (right) following a LP at the indicated CT points. The differences between DC and LP values at each CT point are indicated by asterisks; *p<0.05, **p<0.01, ***p<0.001); n = 4–12 animals/group/CT point.
Figure 2.
Irradiance dependent effect of light on plasma corticosterone and adrenal Per1 and Per2 expression.
The effects of a 30(A, top row), adrenal Per1 mRNA expression (B, middle row), and adrenal Per2 mRNA expression (C, bottom row). Samples were collected 60 min after the beginning of the light pulse during the subjective day at circadian time (CT) 2, CT4, and CT6. The differences between dark controls (0 lux) and light-pulsed animals are indicated by asterisks (*p<0.05, **p<0.01, ***p<0.001), to 35 lux light-pulsed animals by plus signs (+p<0.05, ++p<0.01) and to 350 lux light-pulsed animals by dots (··p<0.01); One-Way ANOVA, n = 4–9 animals/group.
Table 1.
The effect of light stimulation during the subjective day on plasma corticosterone and gene expression in the adrenal.
Figure 3.
Effect of light on plasma ACTH and adrenal StAR and MC2R during the subjective day.
A: The effect of a 30 min light pulse during the subjective day on plasma ACTH. B: Relative mRNA expression of StAR in the adrenal following a 30 min light pulse. C: Relative mRNA expression of MC2R in the adrenal following a 30 min light pulse. Samples were collected 60 min after the beginning of the light pulse of either 35, 350 or 3500 lux during the subjective day at circadian time (CT) 2, CT4, and CT6. No significant differences were observed in plasma ACTH, adrenal StAR mRNA, or adrenal MC2R mRNA expression between light-pulsed and dark control (0 lux) animals at any of the CT points examined; One-Way ANOVA, n = 4–9 animals/group.
Figure 4.
Circadian profiles of adrenal TH and PNMT and following light stimulation during the subjective day.
A: Relative expression of adrenal tyrosine hydroxylase (TH) and phenylethanolamine N-methyltransferase (PNMT) at several circadian time (CT) points. B: Relative expression of adrenal TH and PNMT following a 30 min light-pulse. Samples were collected 60 min after the beginning of the light pulse of either 35, 350 or 3500 lux during the subjective day at circadian time (CT) 2, CT4, and CT6. Significant differences compared to dark controls (0 lux) are indicated by asterisks (*p<0.05, **p<0.01, ***p<0.001), to 35 lux light pulses by plus signs (++p<0.01, +++p<0.001) and to 350 lux light pulses by dots (·p<0.05, ···p<0.001); One-Way ANOVA; n = 4–11 animals/group.