title: Reinforcing effect for corn oil stimulus was concentration dependent in an operant task in mice.
abstract: Corn oil is reported to elicit a conditioned place preference (CPP) in a CPP test in mice. To further investigate a reinforcing effect of corn oil, we studied whether the corn oil acts as a reinforcer under a progressive ratio (PR) schedule in the operant task. BALB/c mice were trained to lever press for sucrose and corn oil. After reaching a stable break-point for 100% corn oil, the PR test was conducted for various concentrations of corn oil (0%-100%). The reinforcing effect of corn oil was increased in a concentration-dependent manner under the PR schedule. A mineral oil and 0.3% xanthan gum as vehicles did not show any reinforcing effect in the PR test, suggesting that oily and viscous texture was not related to the reinforcing property of corn oil. The break-point for corn oil was attenuated by pretreatment with (-)-sulpiride, a D(2) antagonist, in the PR test. On the other hand, SCH23390, a D(1) antagonist, did not influence the break-point. Furthermore, the pretreatment with (-)-sulpiride or SCH23390 did not influence the intake of corn oil in a one-bottle test for 30 min, suggesting that the dopaminergic system is involved in the reinforcing effect but not the consumption of corn oil in mice. In conclusion, operant response to corn oil is concentration-dependently enhanced under the PR schedule. This reinforcing effect of corn oil is at least partly mediated through the dopaminergic systems via D(2) receptors.
authors.affiliation: Laboratory of Nutrition Chemistry, Division of Food Science and Biotechnology, Graduate School of Agriculture, Kyoto University, Kyoto City, Kyoto 606-8502, Japan. yone@kais.kyoto-u.ac.jp
authors.forename: Takeshi
authors.initials: T
authors.lastname: Yoneda
authors.forename: Yuichi
authors.initials: Y
authors.lastname: Taka
authors.forename: Maya
authors.initials: M
authors.lastname: Okamura
authors.forename: Takafumi
authors.initials: T
authors.lastname: Mizushige
authors.forename: Shigenobu
authors.initials: S
authors.lastname: Matsumura
authors.forename: Yasuko
authors.initials: Y
authors.lastname: Manabe
authors.forename: Satoshi
authors.initials: S
authors.lastname: Tsuzuki
authors.forename: Kazuo
authors.initials: K
authors.lastname: Inoue
authors.forename: Tohru
authors.initials: T
authors.lastname: Fushiki
mesh_terms: D000818:Animals; D001552:Benzazepines / Q000494:pharmacology; D003216:Conditioning, Operant / Q000187:drug effects*; D003314:Corn Oil / Q000008:administration & dosage / Q000494:pharmacology*; D004298:Dopamine / Q000502:physiology; D018492:Dopamine Antagonists / Q000494:pharmacology; D065127:Dopamine D2 Receptor Antagonists; D004305:Dose-Response Relationship, Drug; D007202:Indicators and Reagents; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D017447:Receptors, Dopamine D1 / Q000037:antagonists & inhibitors; D012055:Reinforcement Schedule; D012054:Reinforcement, Psychology; D013469:Sulpiride / Q000494:pharmacology
chemical_list: D001552:Benzazepines; D018492:Dopamine Antagonists; D065127:Dopamine D2 Receptor Antagonists; D007202:Indicators and Reagents; D017447:Receptors, Dopamine D1; D013469:Sulpiride; D003314:Corn Oil; D004298:Dopamine