title: Roles of dopamine D1 and D2 receptors in the acquisition and expression of fat-conditioned flavor preferences in rats.
abstract: 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.
authors.affiliation: Neuropsychology Doctoral Sub-Program, The Graduate Center, City University of New York, USA.
authors.forename: J A D
authors.initials: JA
authors.lastname: Dela Cruz
authors.forename: D
authors.initials: D
authors.lastname: Icaza-Cukali
authors.forename: H
authors.initials: H
authors.lastname: Tayabali
authors.forename: C
authors.initials: C
authors.lastname: Sampson
authors.forename: V
authors.initials: V
authors.lastname: Galanopoulos
authors.forename: D
authors.initials: D
authors.lastname: Bamshad
authors.forename: K
authors.initials: K
authors.lastname: Touzani
authors.forename: A
authors.initials: A
authors.lastname: Sclafani
authors.forename: R J
authors.initials: RJ
authors.lastname: Bodnar
mesh_terms: D000818:Animals; D001552:Benzazepines / Q000494:pharmacology; D004041:Dietary Fats; D018492:Dopamine Antagonists / Q000494:pharmacology; D065127:Dopamine D2 Receptor Antagonists; D005518:Food Preferences / Q000187:drug effects / Q000502:physiology*; D008297:Male; D020891:Raclopride / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D017447:Receptors, Dopamine D1 / Q000037:antagonists & inhibitors / Q000378:metabolism*; D017448:Receptors, Dopamine D2 / Q000378:metabolism*; D012439:Saccharin / Q000494:pharmacology; D013549:Sweetening Agents / Q000494:pharmacology; D013649:Taste / Q000187:drug effects / Q000502:physiology*
chemical_list: D001552:Benzazepines; D004041:Dietary Fats; D018492:Dopamine Antagonists; D065127:Dopamine D2 Receptor Antagonists; D017447:Receptors, Dopamine D1; D017448:Receptors, Dopamine D2; C534628:SCH 23390; D013549:Sweetening Agents; D020891:Raclopride; D012439:Saccharin