title: Eating high-fat chow increases the sensitivity of rats to quinpirole-induced discriminative stimulus effects and yawning.
abstract: Discriminative stimulus effects of direct acting dopamine receptor agonists (e.g. quinpirole) appear to be mediated by D3 receptors in free-feeding rats. Free access to high-fat chow increases sensitivity to quinpirole-induced yawning, and this study examined whether eating high-fat chow increases sensitivity to the discriminative stimulus effects of quinpirole. Five rats discriminated between 0.032 mg/kg quinpirole and vehicle while responding under a continuous reinforcement schedule of stimulus shock termination. When rats had free access to high-fat chow (discrimination training was suspended), the quinpirole discrimination dose-response curve shifted leftward, possibly indicating enhanced sensitivity at D3 receptors. In the same rats, both the ascending (mediated by D3 receptors) and descending (mediated by D2 receptors) limbs of the dose-response curve for quinpirole-induced yawning shifted leftward. When rats had free access to a standard chow (discrimination training was suspended), the quinpirole discrimination and yawning dose-response curves did not change. Together with published data showing that the discriminative stimulus effects of quinpirole in free-feeding rats are mediated by D3 receptors and the insensitivity of this effect of quinpirole to food restriction (shown to increase sensitivity to D2 but not D3-mediated effects), these results suggest that the leftward shift of the discrimination dose-response curve when rats eat high-fat chow is likely because of enhanced sensitivity at D3 receptors. Thus, eating high-fat food enhances drug effects in a manner that might impact clinical effects of drugs or vulnerability to drug abuse.
authors: Departments of aPharmacology bPsychiatry, University of Texas Health Science Center at San Antonio, San Antonio, Texas 78229-3900, USA.
authors: Michelle G
authors: MG
authors: Baladi
authors: Charles P
authors: CP
authors: France
mesh_terms: D000821:Animal Feed / Q000009:adverse effects; D000818:Animals; D035841:Behavioral Research; D004041:Dietary Fats / Q000009:adverse effects; D004192:Discrimination, Psychological; D018491:Dopamine Agonists / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D005508:Food Deprivation / Q000502:physiology; D019257:Quinpirole / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D050637:Receptors, Dopamine D3 / Q000819:agonists / Q000378:metabolism; D015000:Yawning / Q000187:drug effects
chemical_list: D004041:Dietary Fats; D018491:Dopamine Agonists; D050637:Receptors, Dopamine D3; D019257:Quinpirole