Cellular and Molecular NeuroscienceResearch PaperRestricted feeding regime affects clock gene expression profiles in the suprachiasmatic nucleus of rats exposed to constant light
Highlights
▶Daily restricted normocaloric feeding regime has no effect on the SCN rhythmicity. ▶We examined whether the feeding regime may affect the SCN under constant light. ▶Under constant light, Per1 and Per2 mRNA exhibited low amplitude rhythms in the SCN. ▶The RF induced circadian rhythms in Rev-erbα and Bmal1 gene expression in the SCN. ▶The SCN molecular clockwork may likely sense signaling delivered by normocaloric food.
Section snippets
Experimental animals
Two-month-old male Wistar rats (Bio Test, Konarovice, Czech Republic) were maintained at a temperature of 21±2 °C under a regime of 12 h of light and 12 h of darkness per day. Light was provided by overhead 40-W fluorescent tubes, illumination was between 50 and 300 lux, depending on the cage position in the animal room. The animals had free access to food and water. On the day of the experiment, the animals were released into LL, that is, the light was not turned off at 18:00 h, the usual time
Effect of LL on locomotor activity
Releasing the rats into LL affected their locomotor activity, as previously demonstrated (Polidarová et al., 2011). The rats started to run with a period of 25.5±0.3 h during the first 14 days of LL (data not shown), and thereafter the rhythmicity gradually deteriorated. Finally, after 30 days in LL, rhythmicity was completely lost. All rats fed ad libitum became completely arrhythmic on the 30th day in LL, as confirmed by periodogram analysis (data demonstrated in the study by Polidarová et
Discussion
These data demonstrate that in the SCN of rats that are behaviorally completely arrhythmic due to 30-day-exposure to LL, not all rhythms in clock gene expression are completely abolished. Although the Bmal1 and Rev-erbα expression did not exhibit circadian rhythmicity, attenuated low amplitude rhythms of Per1 and Per2 expression were suggested. Exposing the rats maintained under LL to RF did not affect the weak rhythm of Per1 and Per2 expression, but affected significantly the rhythms of Bmal1
Conclusion
In conclusion, our data demonstrate that in the SCN of rats behaviorally arrhythmic due to prolonged exposure to LL, low amplitude oscillations in Per1 and Per2 gene expression may be detected. These rhythms, though only borderline significant, may reflect a persistence of synchrony among a small subpopulation of the SCN cells. Moreover, our data demonstrate for the first time that under conditions of prolonged exposure to LL, the RF may synchronize Rev-erbα and Bmal1 gene expression profiles
Acknowledgments
The authors gratefully acknowledge Eva Suchanová and Lenka Hummerová for their excellent technical assistance. The study was supported by grants Nos. 305/09/0321, P303/11/0668, 309/08/H079, LC554, and by Research Project AV0Z 50110509.
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