School of Psychology, University of New South Wales, Australia.
Department of Pharmacology, School of Medical Sciences, University of New South Wales, NSW 2052, Australia.
Behav Brain Res. 2014 May 15;265:132-41. doi: 10.1016/j.bbr.2014.02.027. Epub 2014 Feb 26.
Like people, rodents exposed to energy-rich foods over-eat and become overweight. Removal of this diet activates stress systems, which may explain why people have difficulty dieting. We exposed rats to energy-rich foods in order to identify changes in the brain induced by that diet and by its removal. Sprague Dawley rats were fed lab-chow or an energy-rich cafeteria diet (plus chow). Following 6 or 15 weeks, half of each group was switched to the opposing diet. Rats were culled 48-h later. We measured fat mass, plasma hormones, and assessed brains for mRNA expression of several genes. Cafeteria-fed rats consumed more kilojoules, weighed more and had elevated leptin (plus reduced CORT at 15 weeks) relative to chow-fed rats. Fifteen weeks of cafeteria diet suppressed μ-opioid and CB1 receptor mRNA in the VTA, but elevated amygdala GR, and 6 weeks of cafeteria diet reduced BDNF, compared to chow-fed rats. Rats switched to the cafeteria diet ate similar amounts as rats maintained on the diet, and switching to cafeteria diet after 15 weeks reduced amygdala GR expression. Rats switched to chow ate less than rats maintained on chow, and switching to chow following 15 weeks of cafeteria diet increased hypothalamic CRH mRNA. Therefore, 15 weeks of cafeteria diet produced changes in brain regions implicated in reward processes. Switching these rats to chow activated the HPA axis, while switching chow-fed rats to the cafeteria diet decreased GR expression in the amygdala, a region associated with stress. These findings have implications for dieting in humans.
与人类一样，摄入高热量食物的啮齿类动物也会过度进食并超重。这种饮食会激活应激系统，这也许可以解释为什么人们节食如此困难。我们让老鼠摄入高热量食物，以确定这种饮食及其去除后对大脑的影响。我们用标准实验室饲料（chow）或能量丰富的自助餐厅饮食（cafeteria diet，加上 chow）喂养 Sprague Dawley 大鼠。6 或 15 周后，每组中的一半动物被切换到相反的饮食。48 小时后处死大鼠。我们测量了脂肪量、血浆激素，并评估了几组基因在大脑中的 mRNA 表达。与 chow 喂养的大鼠相比，食用自助餐厅饮食的大鼠摄入了更多的千焦耳，体重增加，并且瘦素水平升高（15 周时皮质醇降低）。15 周的自助餐厅饮食抑制了 VTA 中的 μ 阿片受体和 CB1 受体 mRNA，但增加了杏仁核中的 GR，而 6 周的自助餐厅饮食则降低了 BDNF，与 chow 喂养的大鼠相比。切换到自助餐厅饮食的大鼠的进食量与维持该饮食的大鼠相似，而在 15 周后切换到自助餐厅饮食会降低杏仁核中的 GR 表达。切换到 chow 饮食的大鼠的进食量低于维持 chow 饮食的大鼠，而在 15 周的自助餐厅饮食后切换到 chow 饮食会增加下丘脑的 CRH mRNA。因此，15 周的自助餐厅饮食会改变与奖赏过程相关的大脑区域。这些大鼠切换到 chow 饮食会激活 HPA 轴，而切换到 chow 喂养的大鼠切换到自助餐厅饮食会降低杏仁核中的 GR 表达，杏仁核是与应激相关的区域。这些发现对人类的节食行为具有重要意义。
