title: Ghrelin signaling is not essential for sugar or fat conditioned flavor preferences in mice.
abstract: The oral and post-oral actions of sugar and fat stimulate intake and condition flavor preferences in rodents through a process referred to as appetition. Ghrelin is implicated in food reward processing, and this study investigated its involvement in nutrient conditioning in mice. In Exp. 1 ghrelin receptor-null (GHSR-null) and C57BL/6 wildtype (WT) mice learned to prefer a flavor (CS+) mixed into 8% glucose over another flavor (CS-) mixed into a "sweeter" but non-nutritive 0.1% sucralose+saccharin (S+S) solution. In Exp. 2 treating WT mice with a ghrelin receptor antagonist [(D-Lys3)-GHRP-6] during flavor training did not prevent them from learning to prefer the CS+ glucose over the CS-S+S flavor. GHSR-null and WT mice were trained in Exp. 3 to drink a CS+ paired with intragastric (IG) infusion of 16% glucose and a CS- paired with IG water. Both groups drank more CS+ than CS- in training and preferred the CS+ to CS- in a choice test. The same (Exp. 4) and new (Exp. 5) GHSR-null and WT mice learned to prefer a CS+ flavor paired with IG fat (Intralipid) over a CS- flavor paired with IG water. GHSR-null and WT mice also learned to prefer a CS+ flavor added to 8% fructose over a CS- added to water. Together, these results indicate that ghrelin receptor signaling is not required for flavor preferences conditioned by the oral or post-oral actions of sugar and fat. This contrasts with other findings implicating ghrelin signaling in food reward processing and food-conditioned place preferences.
authors.affiliation: Brooklyn College of CUNY, Brooklyn, NY, USA. Electronic address: ASclafani@gc.cuny.edu.
authors.forename: Anthony
authors.initials: A
authors.lastname: Sclafani
authors.affiliation: Brooklyn College of CUNY, Brooklyn, NY, USA.
authors.forename: Khalid
authors.initials: K
authors.lastname: Touzani
authors.affiliation: Brooklyn College of CUNY, Brooklyn, NY, USA.
authors.forename: Karen
authors.initials: K
authors.lastname: Ackroff
mesh_terms: D000284:Administration, Oral; D000818:Animals; D002241:Carbohydrates / Q000008:administration & dosage*; D003214:Conditioning, Classical / Q000187:drug effects / Q000502:physiology*; D004327:Drinking Behavior / Q000187:drug effects / Q000502:physiology; D005223:Fats / Q000008:administration & dosage*; D005260:Female; D005421:Flavoring Agents / Q000008:administration & dosage; D005508:Food Deprivation / Q000502:physiology; D005518:Food Preferences / Q000187:drug effects / Q000502:physiology*; D005632:Fructose / Q000008:administration & dosage; D054439:Ghrelin / Q000378:metabolism*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D009842:Oligopeptides / Q000494:pharmacology; D054440:Receptors, Ghrelin / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D012439:Saccharin / Q000008:administration & dosage; D015398:Signal Transduction / Q000187:drug effects / Q000235:genetics / Q000502:physiology*; D013549:Sweetening Agents / Q000008:administration & dosage; D013649:Taste / Q000187:drug effects / Q000502:physiology
chemical_list: D002241:Carbohydrates; D005223:Fats; D005421:Flavoring Agents; C520836:GHRP-6, Lys(3)-; D054439:Ghrelin; D009842:Oligopeptides; D054440:Receptors, Ghrelin; D013549:Sweetening Agents; D005632:Fructose; D012439:Saccharin