Excessive consumption of highly palatable foods rich in sugar and fat, often referred to as “junk” or “fast” foods, plays a central role in the development of obesity. The highly palatable characteristics of these foods activate hedonic and motivational mechanisms to promote food-seeking behavior and overeating, which is largely regulated by the brain reward system. Excessive junk food consumption can alter the functioning of this reward system, but exact mechanisms of these changes are still largely unknown. This study investigated whether long-term junk food consumption, in the form of Cafeteria (CAF) diet, can alter the reward system in adult, female Long-Evans rats, and whether different regimes of CAF diet influence the extent of these changes. To this end, rats were exposed to a 6-week diet with either standard chow, or daily access to CAF diet, 30 % restricted but daily access to CAF diet, or one-day-a-week (intermittent) access to CAF diet, after which c-Fos expression in the Nucleus Accumbens (NAc), Prefrontal Cortex (PFC), and Ventral Tegmental Area (VTA) following consumption of a CAF reward of choice was examined. We found that all CAF diet regimes decreased c-Fos expression in the NAc-shell when presented with a CAF reward, while no changes in c-Fos expression upon the different diet regimes were found in the PFC, and possibly the VTA. Our data suggests that long-term junk food exposure can affect the brain reward system, resulting in an attenuated activity of the NAc-shell.

中文翻译：

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自助餐厅饮食消耗后奖励诱导的神经活动的变化

过量食用富含糖和脂肪的美味食品（通常被称为“垃圾”或“快餐”食品）在肥胖的发生中起着核心作用。这些食物的高度适口特性会激活享乐和动机机制，促进寻求食物的行为和暴饮暴食，而这在很大程度上是由大脑奖励系统调节的。过量食用垃圾食品可以改变这种奖励系统的功能，但这些变化的确切机制仍然很大程度上未知。本研究调查了长期以自助餐厅 (CAF) 饮食形式食用垃圾食品是否会改变成年雌性 Long-Evans 大鼠的奖励系统，以及不同的 CAF 饮食方案是否会影响这些变化的程度。为此，大鼠接受为期 6 周的标准饮食，或每天摄入 CAF 饮食，30% 限制但每天摄入 CAF 饮食，或每周一天（间歇性）摄入 CAF 饮食，然后检查消耗选择的 CAF 奖励后伏核 (NAc)、前额皮质 (PFC) 和腹侧被盖区 (VTA) 中的 c-Fos 表达。我们发现，当给予 CAF 奖励时，所有 CAF 饮食方案都会降低 NAc-shell 中的 c-Fos 表达，而在 PFC 和可能的 VTA 中，不同饮食方案的 c-Fos 表达没有变化。我们的数据表明，长期接触垃圾食品会影响大脑奖励系统，导致 NAc 壳的活性减弱。