Reinforcing effects of d-amphetamine: Influence of novel ratios on a progressive-ratio schedule

Rajkumar J. Sevak, William W. Stoops, Paul E.A. Glaser, Lon R. Hays, Craig R. Rush

Research output: Contribution to journalArticlepeer-review

12 Scopus citations


Progressive-ratio schedules are useful for studying the reinforcing effects of drugs. Earlier human laboratory studies showed that d-amphetamine significantly increased break points relative to placebo. However, the magnitude of the increase was modest, which may be attributable to rather high levels of placebo responding. We used novel response requirements in a modified progressive-ratio procedure and hypothesized that the altered range of response requirements would decrease responding for placebo and increase responding for d-amphetamine. Eight participants completed the study. The participants first sampled oral doses of d-amphetamine (0, 8, 16, and 24mg). In subsequent sessions, the participants were offered the opportunity to work for the sampled dose on a modified progressive-ratio procedure with response requirements ranging from 400 to 1800 mouse clicks. A battery of participant-rated drug-effect questionnaires, a performance measure, and cardiovascular measures were included to more fully characterize the effects of d-amphetamine. Placebo maintained low levels of responding. The intermediate dose of d-amphetamine increased responding significantly above placebo levels. d-Amphetamine produced prototypical subject-rated effects that were an orderly function of dose. These data suggest that the modified response requirements resulted in lower levels of placebo taking and a larger separation between the number of placebo and d-amphetamine capsules earned. Behavioural Pharmacology.

Original languageEnglish
Pages (from-to)745-753
Number of pages9
JournalBehavioural Pharmacology
Issue number8
StatePublished - Dec 2010


  • D-amphetamine
  • Drug reinforcement
  • Drug self-administration
  • Human
  • Progressive-ratio
  • Subjective effects


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