Clough Shannon J, Hudson Randall L, Dubocovich Margarita L
Department of Pharmacology & Toxicology, Jacobs School of Medicine and Biomedical Sciences, University at Buffalo, Buffalo, NY 14214, United States.
Department of Physiology & Biophysics, Jacobs School of Medicine and Biomedical Sciences, University at Buffalo, Buffalo, NY 14214, United States.
Behav Brain Res. 2018 May 2;343:28-35. doi: 10.1016/j.bbr.2018.01.027. Epub 2018 Jan 31.
Palatable food is known for its ability to enhance reinforcing responses. Studies have suggested a circadian variation in both drug and natural reinforcement, with each following its own time course. The goal of this study was to determine the role of the MT and MT melatonin receptors in palatable snack food-induced reinforcement, as measured by the conditioned place preference (CPP) paradigm during the light and dark phases. C3H/HeN wild-type mice were trained for snack food-induced CPP at either ZT 6 - 8 (ZT: Zeitgeber time; ZT 0 = lights on), when endogenous melatonin levels are low, or ZT 19 - 21, when melatonin levels are high. These time points also correspond to the high and low points for expression of the circadian gene Period1, respectively. The amount of snack food (chow, Cheetos®, Froot Loops® and Oreos®) consumed was of similar magnitude at both times, however only C3H/HeN mice conditioned to snack food at ZT 6 - 8 developed a place preference. C3H/HeN mice with a genetic deletion of either the MT (MTKO) or MT (MTKO) receptor tested at ZT 6 - 8 did not develop a place preference for snack food. Although the MTKO mice showed a similar amount of snack food consumed when compared to wild-type mice, the MTKO mice consumed significantly less than either genotype. We conclude that in our mouse model snack food-induced CPP is dependent on time of day and the presence of the MT or MT receptors, suggesting a role for melatonin and its receptors in snack food-induced reinforcement.
美味食物以其增强强化反应的能力而闻名。研究表明,药物和天然强化都存在昼夜节律变化,且各自遵循其自身的时间进程。本研究的目的是确定MT和MT褪黑素受体在美味休闲食品诱导的强化中的作用,通过在光照和黑暗阶段的条件性位置偏爱(CPP)范式进行测量。C3H/HeN野生型小鼠在褪黑素水平较低的时间点(ZT 6 - 8,ZT:授时时间;ZT 0 = 开灯)或褪黑素水平较高的时间点(ZT 19 - 21)接受美味休闲食品诱导的CPP训练。这些时间点也分别对应昼夜节律基因Period1表达的高峰和低谷。两个时间点消耗的美味休闲食品(食物、奇多®、果脆圈®和奥利奥®)量相似,但只有在ZT 6 - 8接受美味休闲食品训练的C3H/HeN小鼠产生了位置偏爱。在ZT 6 - 8测试的MT(MTKO)或MT(MTKO)受体基因缺失的C3H/HeN小鼠没有对美味休闲食品产生位置偏爱。虽然与野生型小鼠相比,MTKO小鼠消耗的美味休闲食品量相似,但MTKO小鼠的消耗量明显少于任何一种基因型。我们得出结论,在我们的小鼠模型中,美味休闲食品诱导的CPP取决于一天中的时间以及MT或MT受体的存在,这表明褪黑素及其受体在美味休闲食品诱导的强化中起作用。