Department of Molecular and Developmental Medicine, University of Siena, Via Moro, 2, 53100 Siena, Italy.
Neuroscience. 2013 Apr 16;236:320-31. doi: 10.1016/j.neuroscience.2013.01.027. Epub 2013 Jan 29.
Palatability is the hedonic food component that is considered to override the homeostatic mechanisms that control food intake, and we compared how much effort non food-deprived and food-deprived rats were willing to spend in order to earn a palatable caloric (sucrose) or non-caloric (saccharin) snack. We first studied the dopaminergic response, in terms of dopamine levels and dopamine and cAMP-regulated phosphoprotein Mr 32,000 (DARPP-32) phosphorylation pattern, to two consecutive palatable caloric or non-caloric snacks in the nucleus accumbens shell (NAcS) of non food-deprived and fasted rats. We report that non food-deprived rats developed rapid habituation in the NAcS dopaminergic response to the second consumption of both caloric and non-caloric palatable food, while food-deprived rats developed rapid habituation only to saccharin. Next, we show that in self-administration experiments, non food-deprived rats spent a similar effort when operating for sucrose or saccharin. However, the same rats showed an increased response specifically for sucrose after 18-h fasting. After pre-feeding devaluation, rats reduced their response to sucrose but not for saccharin. These results strengthen the hypothesis that food intake is mainly controlled by palatability in non food-deprived rats and by caloric content in food-deprived rats. Moreover, they show that rapid habituation development was associated with a similar, basal working activity aimed at ingesting both caloric and non-caloric food, as observed in non food-deprived rats consuming sucrose or saccharin and in fasted rats consuming saccharin. Conversely, lack of habituation, as present in fasted rats consuming a caloric food, was associated with extra energy expenditure.
可口性是一种愉悦性的食物成分，被认为可以超越控制食物摄入的体内平衡机制，我们比较了非饥饿和饥饿大鼠为了获得可口的热量（蔗糖）或非热量（糖精）零食而愿意付出多少努力。我们首先研究了多巴胺能反应，即多巴胺水平和多巴胺和 cAMP 调节的磷蛋白 Mr32,000（DARPP-32）磷酸化模式，在非饥饿和禁食大鼠伏隔核壳（NAcS）中连续两次摄入可口的热量或非热量零食。我们报告说，非饥饿大鼠在 NAcS 多巴胺能反应中对第二次摄入热量和非热量可口食物迅速产生习惯化，而饥饿大鼠仅对糖精产生习惯化。接下来，我们表明，在自我给药实验中，非饥饿大鼠在操作蔗糖或糖精时花费了相似的努力。然而，相同的大鼠在 18 小时禁食后表现出对蔗糖的反应增加。在预先喂食减损后，大鼠减少了对蔗糖的反应，但对糖精没有反应。这些结果加强了这样一种假设，即非饥饿大鼠的食物摄入主要受可口性控制，而饥饿大鼠的食物摄入主要受热量含量控制。此外，它们表明，快速习惯化的发展与一种相似的、基础的工作活动有关，这种活动旨在摄入热量和非热量食物，如非饥饿大鼠摄入蔗糖或糖精以及饥饿大鼠摄入糖精时所观察到的那样。相反，缺乏习惯化，如饥饿大鼠摄入热量食物时所表现的那样，与额外的能量消耗有关。
