Effects of dopamine receptor antagonists (D1 and D2) on the demand for smoked cocaine base in rhesus monkeys

Una C. Campbell, Joshua S. Rodefer, Marilyn E Carroll

Research output: Contribution to journalArticlepeer-review

17 Scopus citations

Abstract

Rationale: Previous studies suggest that dopamine antagonists may reduce the reinforcing effects of cocaine. However, the effects of these antagonists on the demand for smoked cocaine base have not been quantified. Objectives: To evaluate the effects of selective D1 (SCH23390) and D2 (raclopride) dopamine receptor antagonists on the demand for smoked cocaine base in rhesus monkeys using a behavioral economic analysis. Methods: Six rhesus monkeys were trained to self-administer smoked cocaine base (1.0 mg/kg/delivery) under chained fixed-ratio (FR) schedules (FR64, 128, 256, 512, 1024 or 2048 for lever presses and FR5 for inhalations) during daily 4-h sessions. A maximum of ten smoke deliveries were available. After 5 days of stable behavior at each FR, SCH 23390 (0.01 and 0.056 mg/kg) or raclopride (0.03 and 0.056 mg/kg) were injected intramuscularly, before each session, for 3 consecutive days. Results: Pretreatment with both antagonists dose- dependently reduced cocaine intake across most FR values tested; however, the decrease in consumption was greater at the higher unit prices that at the unit prices. A statistical estimate of the price (FR) at which maximum responding occurred (P(max)) was decreased during drug pretreatment, indicating weakend reinforcing effectiveness of cocaine. Conclusions: These data suggest that both antagonists reduce the reinforcing effectiveness of smoked cocaine base, and they have a greater effect on cocaine consumption at higher FR values.

Original languageEnglish (US)
Pages (from-to)381-388
Number of pages8
JournalPsychopharmacology
Volume144
Issue number4
DOIs
StatePublished - 1999

Keywords

  • Behavioral economics
  • Cocaine base
  • Crack
  • Demand
  • Dopamine antagonist
  • Drug self-administration
  • Elasticity
  • Raclopride
  • Rhesus monkey
  • SCH 23390
  • Unit price

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