Neuropsychology Doctoral Sub-Program, The Graduate Center, City University of New York, USA.
Neurobiol Learn Mem. 2012 Mar;97(3):332-7. doi: 10.1016/j.nlm.2012.01.008. Epub 2012 Feb 25.
Sugars and fats elicit innate and learned flavor preferences with the latter mediated by flavor-flavor (orosensory) and flavor-nutrient (post-ingestive) processes. Systemic dopamine (DA) D1 (SCH23390: SCH) and D2 (raclopride: RAC), but not opioid antagonists blocked the acquisition and expression of flavor-flavor preferences conditioned by sugars. In addition, systemic D1, but not D2 or opioid antagonists blocked the acquisition of flavor-nutrient preferences conditioned by intragastric (IG) sugar infusions. Given that DA antagonists reduce fat intake, the present study examined whether systemic D1 or D2 antagonists altered the acquisition and/or expression of conditioned flavor preferences (CFP) produced by pairing one novel flavor (CS+, e.g., cherry) with a 3.5% corn oil (CO: fat) solution relative to another flavor (CS-, e.g., grape) paired with a 0.9% CO solution. In an expression study, food-restricted rats were trained to drink either flavored 3.5% or 0.9% CO solutions on alternate days. Subsequent two-bottle tests with the CS+ and CS- flavors mixed in 0.9% CO solutions occurred 0.5h after systemic administration of vehicle (VEH), SCH (50-800 nmol/kg) or RAC (50-800 nmol/kg). The rats displayed a robust CS+ preference following VEH treatment (87-88%) the expression of which was attenuated by treatment with moderate doses of RAC, and to a lesser degree, SCH. In an acquisition study, six groups of rats received VEH, SCH (25, 50, 200 nmol/kg) or RAC (50, 200 nmol/kg) 0.5 h prior to 1-bottle training trials with CS+ flavored 3.5% and CS- flavored 0.9% (CS-) CO solutions. A seventh Limited VEH group was trained with its training intakes limited to that of the SCH and RAC groups. Subsequent two-bottle tests were conducted with the CS+ and CS- flavors presented in 0.9% CO without injections. Significant and persistent CS+ preferences were observed in VEH (75-82%), Limited VEH (70-88%), SCH25 (75-84%), SCH50 (64-87%), SCH200 (78-91%) and RAC200 (74-91%) groups. In contrast, the group trained with RAC50 displayed a significant initial CS+ preference (76%) which declined over testing to 61%. These data indicate limited DA D1 and D2 receptor signaling involvement in the expression and acquisition of a fat-CFP relative to previous robust effects for sugar-CFP.
糖和脂肪会引起先天和后天的口味偏好，而后者则通过味道-味道（口腔感觉）和味道-营养（摄后）过程来介导。系统多巴胺（DA）D1（SCH23390：SCH）和 D2（raclopride：RAC），但不是阿片受体拮抗剂，阻断了由糖调节的味道-味道偏好的获得和表达。此外，系统 D1，但不是 D2 或阿片受体拮抗剂，阻断了由胃内（IG）糖输注调节的味道-营养偏好的获得。鉴于 DA 拮抗剂会减少脂肪摄入，本研究检测了系统 D1 或 D2 拮抗剂是否会改变与将一种新口味（CS+，例如樱桃）与 3.5%玉米油（CO：脂肪）溶液配对相关的条件口味偏好（CFP）的获得和/或表达与另一种口味（CS-，例如葡萄）与 0.9% CO 溶液配对。在表达研究中，限制食物摄入的大鼠被训练在交替的日子里饮用带有风味的 3.5%或 0.9% CO 溶液。在系统给予载体（VEH）、SCH（50-800 nmol/kg）或 RAC（50-800 nmol/kg）后 0.5 小时，用含有 0.9% CO 的 CS+和 CS-混合的两瓶进行测试。在 VEH 处理后，大鼠表现出强烈的 CS+偏好（87-88%），而用中等剂量的 RAC 处理，以及在较小程度上用 SCH 处理，这种偏好表达会减弱。在获得研究中，六组大鼠在 1 瓶训练试验前 0.5 小时接受 VEH、SCH（25、50、200 nmol/kg）或 RAC（50、200 nmol/kg）处理，用 CS+调味的 3.5%和 CS-调味的 0.9%（CS-）CO 溶液进行训练。第七个 Limited VEH 组与 SCH 和 RAC 组的训练摄入量限制在一起进行训练。随后，在没有注射的情况下，用含有 0.9% CO 的 CS+和 CS-进行两瓶测试。在 VEH（75-82%）、Limited VEH（70-88%）、SCH25（75-84%）、SCH50（64-87%）、SCH200（78-91%）和 RAC200（74-91%）组中观察到显著且持久的 CS+偏好。相比之下，用 RAC50 训练的组表现出显著的初始 CS+偏好（76%），但在测试过程中下降到 61%。这些数据表明，与先前对糖-CFP 的强烈影响相比，多巴胺 D1 和 D2 受体信号的有限参与对脂肪-CFP 的表达和获得有影响。
