title: Feeding condition and the relative contribution of different dopamine receptor subtypes to the discriminative stimulus effects of cocaine in rats.
abstract: BACKGROUND
  The contribution of dopamine receptor subtypes in mediating the discriminative stimulus effects of cocaine is not fully established. Many drug discrimination studies use food to maintain responding, necessitating food restriction, which can alter drug effects.
  
  
  OBJECTIVE
  This study established stimulus control with cocaine (10 mg/kg) in free-feeding and food-restricted rats responding under a schedule of stimulus shock termination (SST) and in food-restricted rats responding under a schedule of food presentation to examine whether feeding condition or the reinforcer used to maintain responding impacts the effects of cocaine.
  
  
  METHODS
  Dopamine receptor agonists and antagonists were examined for their ability to mimic or attenuate, respectively, the effects of cocaine.
  
  
  RESULTS
  Apomorphine, quinpirole, and lisuride occasioned >90 % responding on the cocaine-associated lever in free-feeding rats responding under a schedule of SST; apomorphine, but not quinpirole or lisuride, occasioned >90 % responding on the cocaine lever in food-restricted rats responding under a schedule of SST. In food-restricted rats responding for food these drugs occasioned little cocaine lever responding and were comparatively more potent in decreasing responding. In free-feeding rats, the effects of cocaine were attenuated by the D2/D3 receptor antagonist raclopride and the D3 receptor-selective antagonist PG01037. In food-restricted rats, raclopride and the D2 receptor-selective antagonist L-741,626 attenuated the effects of cocaine. Raclopride antagonized quinpirole in all groups while PG01037 antagonized quinpirole only in free-feeding rats.
  
  
  CONCLUSIONS
  These results demonstrate significant differences in the discriminative stimulus of cocaine that are due to feeding conditions and not to the use of different reinforcers across procedures.
authors.affiliation: Department of Pharmacology, University of Texas Health Science Center at San Antonio, 7703 Floyd Curl Drive, Mail Code 7764, San Antonio, TX, 78229, 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: D000818:Animals; D001058:Apomorphine / Q000494:pharmacology; D001549:Benzamides / Q000494:pharmacology; D003042:Cocaine / Q000494:pharmacology*; D003216:Conditioning, Operant / Q000187:drug effects / Q000502:physiology; D004192:Discrimination, Psychological / Q000187:drug effects* / Q000502:physiology; D018491:Dopamine Agonists / Q000494:pharmacology*; D018492:Dopamine Antagonists / Q000494:pharmacology*; D018765:Dopamine Uptake Inhibitors / Q000494:pharmacology*; D004597:Electroshock; D005508:Food Deprivation / Q000502:physiology*; D007211:Indoles / Q000494:pharmacology; D008090:Lisuride / Q000494:pharmacology; D008297:Male; D010880:Piperidines / Q000494:pharmacology; D011725:Pyridines / Q000494:pharmacology; D019257:Quinpirole / Q000494:pharmacology; D020891:Raclopride / Q000494:pharmacology; D017207:Rats, Sprague-Dawley; D012054:Reinforcement, Psychology
chemical_list: D001549:Benzamides; D018491:Dopamine Agonists; D018492:Dopamine Antagonists; D018765:Dopamine Uptake Inhibitors; D007211:Indoles; C497150:N-(4-(4-(2,3-dichlorophenyl)piperazin-1-yl)but-2-enyl)-4-pyridine-2-ylbenzamide; D010880:Piperidines; D011725:Pyridines; D019257:Quinpirole; D020891:Raclopride; C104750:3-(4-(4-chlorophenyl-4-hydroxypiperidino)methyl)indole; D008090:Lisuride; D003042:Cocaine; D001058:Apomorphine
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