Limits...
Photic and pineal modulation of food anticipatory circadian activity rhythms in rodents.

Patton DF, Parfyonov M, Gourmelen S, Opiol H, Pavlovski I, Marchant EG, Challet E, Mistlberger RE - PLoS ONE (2013)

Bottom Line: Nonetheless, light could reduce the duration or magnitude of FAA.In both species, FAA was significantly and reversibly enhanced in the skeleton photoperiod compared to the full photoperiod.These results indicate that procedures affecting behavioral responses to light can significantly alter the magnitude of food anticipatory rhythms in rodents.

View Article: PubMed Central - PubMed

Affiliation: Department of Psychology, Simon Fraser University, Burnaby, British Columbia, Canada.

ABSTRACT
Restricted daily feeding schedules entrain circadian oscillators that generate food anticipatory activity (FAA) rhythms in nocturnal rodents. The location of food-entrainable oscillators (FEOs) necessary for FAA remains uncertain. The most common procedure for inducing circadian FAA is to limit food access to a few hours in the middle of the light period, when activity levels are normally low. Although light at night suppresses activity (negative masking) in nocturnal rodents, it does not prevent the expression of daytime FAA. Nonetheless, light could reduce the duration or magnitude of FAA. If so, then neural or genetic ablations designed to identify components of the food-entrainable circadian system could alter the expression of FAA by affecting behavioral responses to light. To assess the plausibility of light as a potential mediating variable in studies of FAA mechanisms, we quantified FAA in rats and mice alternately maintained in a standard full photoperiod (12h of light/day) and in a skeleton photoperiod (two 60 min light pulses simulating dawn and dusk). In both species, FAA was significantly and reversibly enhanced in the skeleton photoperiod compared to the full photoperiod. In a third experiment, FAA was found to be significantly attenuated in rats by pinealectomy, a procedure that has been reported to enhance some effects of light on behavioral circadian rhythms. These results indicate that procedures affecting behavioral responses to light can significantly alter the magnitude of food anticipatory rhythms in rodents.

Show MeSH

Related in: MedlinePlus

Group mean (± sem) waveforms of activity measured by motion sensors in pinealectomized (PnX) and sham rats during scheduled feeding.A. ZT6-9 mealtime; B. Food deprivation day in constant dark after last ZT6-9 feeding; C. ZT9-12 mealtime, D. ZT3-6 mealtime, E. Food deprivation day in constant dark after last ZT3-6 feeding; F. Group mean (± sem) melatonin levels in sham (solid black bar) and PnX (red line) rats from serum samples collected 2–4 hours after lights-off, when pineal melatonin secretion is normally high. In Panels A, C and D, mealtime is highlighted in green and the LD cycle is indicated by yellow and black bars along the horizontal axis.
© Copyright Policy
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC3852709&req=5

pone-0081588-g006: Group mean (± sem) waveforms of activity measured by motion sensors in pinealectomized (PnX) and sham rats during scheduled feeding.A. ZT6-9 mealtime; B. Food deprivation day in constant dark after last ZT6-9 feeding; C. ZT9-12 mealtime, D. ZT3-6 mealtime, E. Food deprivation day in constant dark after last ZT3-6 feeding; F. Group mean (± sem) melatonin levels in sham (solid black bar) and PnX (red line) rats from serum samples collected 2–4 hours after lights-off, when pineal melatonin secretion is normally high. In Panels A, C and D, mealtime is highlighted in green and the LD cycle is indicated by yellow and black bars along the horizontal axis.

Mentions: Food anticipatory activity. Despite the absence of predicted group differences in masking responses to light, during restricted daytime feeding there was a significant effect of group on FAA counts (F (1,15)  = 4.68, p<.05) and FAA ratios (F(1,15)  = 14.40, p = .0018). Food was first provided from ZT6-9, and then shifted to ZT9-12 and ZT3-6 at 3 week intervals. Both groups exhibited robust FAA, beginning 2-3 h before each of mealtime (Fig. 6). Total daily activity did not differ, but the sham rats exhibited more activity during the 2-h prior to each mealtime and a significantly higher anticipation ratio (Fig. 7a,b). When the lights were turned off for one day, the group differences in food anticipation counts and ratios in the ZT6-9 and ZT3-6 conditions were absent. Notably, with the lights off prior to mealtime, FAA counts and ratios increased in both groups, but more so in the PnX group (Fig. 7a,b).


Photic and pineal modulation of food anticipatory circadian activity rhythms in rodents.

Patton DF, Parfyonov M, Gourmelen S, Opiol H, Pavlovski I, Marchant EG, Challet E, Mistlberger RE - PLoS ONE (2013)

Group mean (± sem) waveforms of activity measured by motion sensors in pinealectomized (PnX) and sham rats during scheduled feeding.A. ZT6-9 mealtime; B. Food deprivation day in constant dark after last ZT6-9 feeding; C. ZT9-12 mealtime, D. ZT3-6 mealtime, E. Food deprivation day in constant dark after last ZT3-6 feeding; F. Group mean (± sem) melatonin levels in sham (solid black bar) and PnX (red line) rats from serum samples collected 2–4 hours after lights-off, when pineal melatonin secretion is normally high. In Panels A, C and D, mealtime is highlighted in green and the LD cycle is indicated by yellow and black bars along the horizontal axis.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3852709&req=5

pone-0081588-g006: Group mean (± sem) waveforms of activity measured by motion sensors in pinealectomized (PnX) and sham rats during scheduled feeding.A. ZT6-9 mealtime; B. Food deprivation day in constant dark after last ZT6-9 feeding; C. ZT9-12 mealtime, D. ZT3-6 mealtime, E. Food deprivation day in constant dark after last ZT3-6 feeding; F. Group mean (± sem) melatonin levels in sham (solid black bar) and PnX (red line) rats from serum samples collected 2–4 hours after lights-off, when pineal melatonin secretion is normally high. In Panels A, C and D, mealtime is highlighted in green and the LD cycle is indicated by yellow and black bars along the horizontal axis.
Mentions: Food anticipatory activity. Despite the absence of predicted group differences in masking responses to light, during restricted daytime feeding there was a significant effect of group on FAA counts (F (1,15)  = 4.68, p<.05) and FAA ratios (F(1,15)  = 14.40, p = .0018). Food was first provided from ZT6-9, and then shifted to ZT9-12 and ZT3-6 at 3 week intervals. Both groups exhibited robust FAA, beginning 2-3 h before each of mealtime (Fig. 6). Total daily activity did not differ, but the sham rats exhibited more activity during the 2-h prior to each mealtime and a significantly higher anticipation ratio (Fig. 7a,b). When the lights were turned off for one day, the group differences in food anticipation counts and ratios in the ZT6-9 and ZT3-6 conditions were absent. Notably, with the lights off prior to mealtime, FAA counts and ratios increased in both groups, but more so in the PnX group (Fig. 7a,b).

Bottom Line: Nonetheless, light could reduce the duration or magnitude of FAA.In both species, FAA was significantly and reversibly enhanced in the skeleton photoperiod compared to the full photoperiod.These results indicate that procedures affecting behavioral responses to light can significantly alter the magnitude of food anticipatory rhythms in rodents.

View Article: PubMed Central - PubMed

Affiliation: Department of Psychology, Simon Fraser University, Burnaby, British Columbia, Canada.

ABSTRACT
Restricted daily feeding schedules entrain circadian oscillators that generate food anticipatory activity (FAA) rhythms in nocturnal rodents. The location of food-entrainable oscillators (FEOs) necessary for FAA remains uncertain. The most common procedure for inducing circadian FAA is to limit food access to a few hours in the middle of the light period, when activity levels are normally low. Although light at night suppresses activity (negative masking) in nocturnal rodents, it does not prevent the expression of daytime FAA. Nonetheless, light could reduce the duration or magnitude of FAA. If so, then neural or genetic ablations designed to identify components of the food-entrainable circadian system could alter the expression of FAA by affecting behavioral responses to light. To assess the plausibility of light as a potential mediating variable in studies of FAA mechanisms, we quantified FAA in rats and mice alternately maintained in a standard full photoperiod (12h of light/day) and in a skeleton photoperiod (two 60 min light pulses simulating dawn and dusk). In both species, FAA was significantly and reversibly enhanced in the skeleton photoperiod compared to the full photoperiod. In a third experiment, FAA was found to be significantly attenuated in rats by pinealectomy, a procedure that has been reported to enhance some effects of light on behavioral circadian rhythms. These results indicate that procedures affecting behavioral responses to light can significantly alter the magnitude of food anticipatory rhythms in rodents.

Show MeSH
Related in: MedlinePlus