title: Choice for response alternatives differing in reinforcement frequency in dopamine D2 receptor mutant and Swiss-Webster mice.
abstract: BACKGROUND
  A previous study showed that dopamine (DA) D2 receptors (D2Rs) are involved in the reinforcing effectiveness of food, but the specific involvement of DA D2Rs in choice among food reinforcers remains unclear.
  
  
  OBJECTIVE
  The current study used genetic and pharmacological approaches to assess the role of D2Rs in choice among food-reinforcement frequencies using the generalized matching law (GML), which specifies that logged response and time allocation ratios vary linearly with logged reinforcer ratios.
  
  
  METHODS
  Congenic D2R knockout (KO) and wild-type (WT) mice were exposed to concurrent variable-interval schedules of reinforcement with scheduled relative-reinforcement rates from 4:1 to 1:4. Effects of the D2R antagonist (-)-eticlopride (0.1-1.0 mg/kg) were assessed in Swiss-Webster mice.
  
  
  RESULTS
  Response and time allocation ratios were related to obtained reinforcement ratios as predicted by the GML. GML fits accounted for ≥ 92 % of the variance in allocation ratios and did not differ in D2R KO and WT mice. Similarly, there were no significant effects of (-)-eticlopride dose on GML fits, despite effects on overall response rates.
  
  
  CONCLUSIONS
  The current results demonstrate that neither deletion nor acute blockade of D2Rs affects choice among response alternatives varying in food-reinforcement frequencies. Because previously published results suggest a role of D2Rs in choice between response alternatives differing in reinforcer magnitude and delay or magnitude and probability, the current findings suggest that D2Rs play a role in choice only among certain parameters of reinforcement. Furthermore, these findings suggest parameters of reinforcement may only be fungible in a complex manner.
authors.affiliation: Department of Educational Psychology and Leadership, Texas Tech University, Lubbock, TX, 79410, USA, paul.soto@ttu.edu.
authors.forename: Paul L
authors.initials: PL
authors.lastname: Soto
authors.forename: Takato
authors.initials: T
authors.lastname: Hiranita
authors.forename: David K
authors.initials: DK
authors.lastname: Grandy
authors.forename: Jonathan L
authors.initials: JL
authors.lastname: Katz
mesh_terms: D000465:Algorithms; D000818:Animals; D002755:Choice Behavior / Q000187:drug effects*; D003216:Conditioning, Operant / Q000187:drug effects*; D018492:Dopamine Antagonists / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D005502:Food; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D009154:Mutation / Q000502:physiology*; D017448:Receptors, Dopamine D2 / Q000235:genetics*; D012055:Reinforcement Schedule; D012054:Reinforcement, Psychology; D012457:Salicylamides / Q000494:pharmacology
chemical_list: D018492:Dopamine Antagonists; D017448:Receptors, Dopamine D2; D012457:Salicylamides; C045989:eticlopride