title: Influence of body weight and type of chow on the sensitivity of rats to the behavioral effects of the direct-acting dopamine-receptor agonist quinpirole.
abstract: BACKGROUND
  Amount and type of food can alter dopamine systems and sensitivity to drugs acting on those systems.
  
  
  OBJECTIVE
  This study examined whether changes in body weight, food type, or both body weight and food type contribute to these effects.
  
  
  METHODS
  Rats had free or restricted access (increasing, decreasing, or maintaining body weight) to standard (5.7% fat) or high-fat (34.3%) chow.
  
  
  RESULTS
  In rats gaining weight with restricted or free access to high-fat chow, both limbs of the quinpirole yawning dose-response curve (0.0032-0.32 mg/kg) shifted leftward compared with rats eating standard chow. Restricting access to standard or high-fat chow (maintaining or decreasing body weight) decreased or eliminated quinpirole-induced yawning; within 1 week of resuming free feeding, sensitivity to quinpirole was restored, although the descending limb of the dose-response curve was shifted leftward in rats eating high-fat chow. These are not likely pharmacokinetic differences because quinpirole-induced hypothermia was not different among groups. PG01037 and L-741,626 antagonized the ascending and descending limbs of the quinpirole dose-response curve in rats eating high-fat chow, indicating D3 and D2 receptor mediation, respectively. Rats eating high-fat chow also developed insulin resistance.
  
  
  CONCLUSIONS
  These results show that amount and type of chow alter sensitivity to a direct-acting dopamine-receptor agonist with the impact of each factor depending on whether body weight increases, decreases, or is maintained. These data demonstrate that feeding conditions, perhaps related to insulin and insulin sensitivity, profoundly impact the actions of drugs acting on dopamine systems.
authors.affiliation: Department of Pharmacology, University of Texas Health Science Center at San Antonio, 7703 Floyd Curl Drive, San Antonio, TX 78229-3900, USA.
authors.forename: Michelle G
authors.initials: MG
authors.lastname: Baladi
authors.forename: Amy H
authors.initials: AH
authors.lastname: Newman
authors.forename: Charles P
authors.initials: CP
authors.lastname: France
mesh_terms: D000821:Animal Feed / Q000009:adverse effects; D000818:Animals; D001522:Behavior, Animal / Q000187:drug effects*; D001831:Body Temperature / Q000187:drug effects; D001835:Body Weight / Q000187:drug effects*; D004041:Dietary Fats / Q000008:administration & dosage / Q000009:adverse effects; D018491:Dopamine Agonists / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D018565:Food-Drug Interactions; D008297:Male; D019257:Quinpirole / Q000494:pharmacology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D011954:Receptors, Dopamine / Q000378:metabolism*; D015000:Yawning / Q000187:drug effects
chemical_list: D004041:Dietary Fats; D018491:Dopamine Agonists; D011954:Receptors, Dopamine; D019257:Quinpirole