Department of Psychology, Simon Fraser University, Burnaby, British Columbia, Canada.
PLoS One. 2013 Dec 4;8(12):e81588. doi: 10.1371/journal.pone.0081588. eCollection 2013.
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.
限制每日进食时间会使昼夜节律振荡器同步，从而产生夜间啮齿动物的食物预期活动（FAA）节律。产生 FAA 的食物可诱导振荡器（FEO）的位置仍不确定。诱导昼夜 FAA 的最常见方法是将食物限制在光照期中间的几个小时内，此时活动水平通常较低。尽管夜间的光会抑制夜间啮齿动物的活动（负掩蔽），但它并不能阻止白天 FAA 的表达。尽管如此，光可能会减少 FAA 的持续时间或幅度。如果是这样，那么旨在识别食物可诱导的昼夜节律系统成分的神经或遗传消融术可能会通过影响对光的行为反应来改变 FAA 的表达。为了评估光作为 FAA 机制研究中潜在的中介变量的可能性，我们在标准全光照周期（每天 12 小时光照）和骨架光照周期（模拟黎明和黄昏的两个 60 分钟光脉冲）中交替维持大鼠和小鼠，对 FAA 进行了定量评估。在这两个物种中，与全光照周期相比，骨架光照周期中的 FAA 明显增强且具有可逆性。在第三个实验中，发现松果切除术显著减弱了大鼠的 FAA，松果切除术已被报道增强了光对行为昼夜节律的一些影响。这些结果表明，影响对光的行为反应的程序可以显著改变啮齿动物食物预期节律的幅度。
