A number of studies implicate biogenic amines in regulating circadian rhythms. In particular, dopamine and serotonin influence the entrainment of circadian rhythms to daily food availability. To study circadian entrainment to feeding, food availability is typically restricted to a short period within the light cycle daily. This results in a notable increase in pre-meal activity, termed “food anticipatory activity” (FAA), which typically develops within about 1 week of scheduled feeding. Several studies have implicated serotonin as a negative regulator of FAA: (1) aged rats treated with serotonin 5-HT2 and 3 receptor antagonists showed enhanced FAA, (2) mice lacking for the 2C serotonin receptor demonstrate enhanced FAA, and (3) pharmacologically increased serotonin levels suppressed FAA while decreased serotonin levels enhanced FAA in mice. We sought to confirm and extend these findings using genetic models with impairments in central serotonin production or re-uptake, but were surprised to find that both serotonin transporter (Slc6a4) and tryptophan hydroxylase-2 knockout mice demonstrated a normal behavioral response to timed, calorie restricted feeding. Our data suggest that FAA is largely independent of central serotonin and/or serotonin reuptake and that serotonin may not be a robust negative regulator of FAA.

许多研究表明生物胺在调节昼夜节律中起作用。特别是多巴胺和5-羟色胺会影响昼夜节律对每日食物供应的影响。为了研究昼夜节食对食物的夹带，通常在每天的光周期内将食物供应限制在短时间内。这导致餐前活动（称为“食品预期活动”（FAA））显着增加，通常在预定的进食后1周内发展。几项研究表明，血清素是FAA的负调节剂：（1）用血清素5-HT2和3种受体拮抗剂治疗的成年大鼠显示FAA增强，（2）缺乏2C血清素受体的小鼠显示FAA增强，以及（3）药理作用血清素水平的升高会抑制FAA，而血清素水平的降低会增强小鼠的FAA。血清素转运蛋白 （Slc6a4）和 色氨酸羟化酶2剔除小鼠表现出对定时限卡路里喂养的正常行为反应。我们的数据表明，FAA在很大程度上独立于中央5-羟色胺和/或5-羟色胺的再摄取，并且5-羟色胺可能不是FAA的强大负调节剂。