Roles of dopamine D1 and D2 receptors in the acquisition and expression of fat-conditioned flavor preferences in rats

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• 作者：J.A.D. Dela Cruz^a ; D. Icaza-Cukali^c ; H. Tayabali^c ; C. Sampson^c ; V. Galanopoulos^c ; D. Bamshad^c ; K. Touzani^d ; A. Sclafani^a ; ^b ; ^d ; R.J. Bodnar^a ; ^c ; ^{Richard.Bodnar@qc.cuny.edu}
• 关键词：Corn oil ; SCH23390 ; Raclopride ; Learning
• 刊名：Neurobiology of Learning and Memory
• 出版年：2012
• 期刊代码：81_10747427
• 类别：neu
• 出版时间：March, 2012
• 卷：97
• 期：3
• 页码：332-337
• 文件大小：448 K

摘要

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鈭? 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鈭?flavors mixed in 0.9%CO solutions occurred 0.5 h 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鈭?flavored 0.9%(CS鈭? 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鈭?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.