| Abstract No.: | C-E3164 |
| Country: | Canada |
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| Title: | EXPRESSION OF THE CLOCK PROTEIN PERIOD2 IN THE LIMBIC FOREBRAIN IS MODULATED BY FOOD ‘ANTICIPATION’ AND THE TIME OF DAY MEALS ARE PRESENTED |
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| Authors/Affiliations: | 1 Michael Verwey*; 1 Germain YM Lam; 1 Shimon Amir;
1 Concordia University, Montreal, QC, Canada
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| Content: | Objective: Circadian rhythms in gene expression are observed throughout the brain, however, the functional consequence(s) of many of these oscillations remain unknown. The main objective of this work was to study how changes in behavioral and metabolic rhythms (triggered by manipulations of food availability) influence the expression patterns of the clock protein Period2 (PER2) in several nuclei of the limbic forebrain.
Materials and Methods: Male Wistar rats were housed individually in cages equipped with running wheels, under a 12 hour:12 hour light-dark cycle and had free access to food and water for at least 2 weeks prior to the experiment. Control rats continued to receive free access to food, while the experimental rats were fasted and received a 2 hour meal at unpredictable mealtimes each day for 10 days. Experimental rats were divided into three groups based on the variation of the unpredictable meal, the time the 2-hour meal began varied within the 12 hours of light, the 12 hours of dark or across the entire 24 hour cycle. Rats (n=3-4/time/group) were perfused at zeitgeber times (ZT; ZT 0 denotes lights-on and ZT 12 lights-off) 1, 7 (1 and 7 hours after lights-on), 13, or 19 (1 and 7 hours after lights-off). Brains were sliced and cells expressing the clock protein PER2 were stained by immunocytochemistry.
Results: Consistent with previous findings, the ad libitum fed control group showed a robust circadian rhythm in PER2 expression across the day – in the suprachiasmatic nucleus (SCN), the oval nucleus of the bed nucleus of the stria terminalis (BNSTov), the central nucleus of the amygdala (CEA), the basolateral amygdala (BLA) and the dentate gyrus (DG). These areas are important in the regulation and control of diverse emotional, homeostatic and motivational processes, including feeding.
In contrast, when rats received a restricted 2-hour ‘meal’ at variable mealtimes each day, this blunted the circadian rhythm of PER2 expression in most structures. Specifically, in the BNSTov and CEA the amplitude of the rhythm in PER2 expression was greatly reduced in all variable feeding conditions. However, PER2 expression in the BLA and DG was disrupted principally in the daytime variable feeding condition. For the most part, PER2 expression in the SCN was unaffected by manipulations of feeding.
Conclusions: In summary, ‘anticipatory’ activity appears to be necessary for coherent shifts of PER2 expression in the BNSTov and CEA, while PER2 expression in the BLA and DG seems to be linked to the time of day meals are presented. |
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