Department of Psychology and Program in Neuroscience, Florida State University, Tallahassee, FL, USA.
Department of Psychology and Program in Neuroscience, Florida State University, Tallahassee, FL, USA.
Physiol Behav. 2022 May 1;248:113730. doi: 10.1016/j.physbeh.2022.113730. Epub 2022 Feb 8.
In rodents, repeated single-bottle exposures to distinctly flavored isocaloric glucose and fructose solutions, two sugars with different metabolic pathways, eventually lead to a preference for the former. Because Roux-en-Y gastric bypass (RYGB) surgery decreases preference for and intake of sugar solutions in rats, we tested whether RYGB would curtail the conditioning of a preference for a glucose-paired vs. fructose-paired flavor. RYGB (♂ n=11; ♀ n=10) and sham-operated (SHAM; ♂ n=9; ♀ n=10) rats were trained with a single bottle (30 min/day) containing 8% glucose solution flavored with either 0.05% grape or cherry Kool-Aid (Glu/CS) or 8% fructose solution with the alternative Kool-Aid flavor (Fru/CS) in an alternating fashion for 8 days. To determine baseline preferences, a 4-day 30-min two-bottle test was used to assess preference for Glu/CS vs. Fru/CS before training. After training, 2-day 30-min two-bottle tests assessed preference for the a) Glu/CS (CS-flavored 8% glucose solution) vs Fru/CS (CS-flavored 8% fructose solution), b) CS- vs. CS-flavored mixture of 4% glucose & 4% fructose (isocaloric), c) CS- vs. CS-flavored 0.2% saccharin ("sweet", no calories), and d) CS- vs. CS-flavored water. During training, only male SHAM rats demonstrated progressively increased intake of Glu/CS over Fru/CS, and female SHAM rats displayed a trend. RYGB eliminated any difference in single-bottle intake of these solutions during training, regardless of sex. Like their male and female SHAM counterparts, male RYGB rats displayed a conditioned preference for the CS-associated stimulus in Tests 1-3. Although female RYGB rats displayed acquisition of the conditioned flavor preference in Test 1, unlike the other groups, when the differential sugar cue between the two solutions was removed in Tests 2 and 3, female rats did not display a CS preference. When the sugar and sweetener cues were both removed on Test 4, all groups displayed some generalization decrement. Thus, RYGB does not compromise the ability of rats to learn and express a glucose- vs. fructose-associated conditioned flavor preference when the exact CS used in training is presented in testing. The mechanistic basis for the sex difference in the effect of RYGB on the generalization decrement observed in this type of flavor preference learning warrants further study.
在啮齿动物中，反复单一瓶暴露于明显风味的等热量葡萄糖和果糖溶液中，这两种糖具有不同的代谢途径，最终导致对前者的偏好。由于 Roux-en-Y 胃旁路（RYGB）手术降低了大鼠对糖溶液的偏好和摄入，我们测试了 RYGB 是否会减少对葡萄糖配对与果糖配对风味的条件偏好。RYGB（♂n=11；♀n=10）和假手术（SHAM；♂n=9；♀n=10）大鼠接受单一瓶子（30 分钟/天）训练，其中包含 8%葡萄糖溶液，味道为 0.05%葡萄或樱桃 Kool-Aid（Glu/CS）或 8%果糖溶液，交替使用另一种 Kool-Aid 风味（Fru/CS），持续 8 天。为了确定基线偏好，使用 4 天 30 分钟的双瓶测试来评估训练前对 Glu/CS 与 Fru/CS 的偏好。在训练后，进行 2 天 30 分钟的双瓶测试，以评估对以下各项的偏好：a）Glu/CS（CS 调味的 8%葡萄糖溶液）与 Fru/CS（CS 调味的 8%果糖溶液），b）CS-与 CS 调味的 4%葡萄糖和 4%果糖混合物（等热量），c）CS-与 CS 调味的 0.2%糖精（“甜”，无热量），以及 d）CS-与 CS 调味的水。在训练过程中，只有雄性 SHAM 大鼠表现出对 Glu/CS 的摄入量逐渐增加，而雌性 SHAM 大鼠则表现出趋势。RYGB 消除了训练过程中对这些溶液的单一瓶摄入差异，无论性别如何。与雄性和雌性 SHAM 对照组一样，雄性 RYGB 大鼠在测试 1-3 中表现出对 CS 相关刺激的条件偏好。尽管雌性 RYGB 大鼠在测试 1 中表现出获得了条件风味偏好，但与其他组不同的是，当两种溶液之间的差异糖线索在测试 2 和 3 中被移除时，雌性大鼠没有表现出 CS 偏好。当测试 4 中同时移除糖和甜味剂线索时，所有组都表现出一些概括性下降。因此，当在测试中呈现训练中使用的精确 CS 时，RYGB 不会损害大鼠学习和表达葡萄糖与果糖相关条件风味偏好的能力。RYGB 对这种类型的风味偏好学习中观察到的概括性下降的影响在性别上的差异的机制基础值得进一步研究。
