EFFECTS OF D-AMPHETAMINE AND DIAZEPAM ON FIXED-INTERVAL, FIXED-RATIO RESPONDING IN HUMANS

  • 1 January 1982
    • journal article
    • research article
    • Vol. 221  (2) , 373-383
Abstract
Human operant responding, maintained under a multiple fixed-ratio (FR) 30 fixed-interval (FI) 5 min schedule of point presentation was differentially sensitive to the effects of d-amphetamine and diazepam. d-Amphetamine (5-20 mg)increased rates of FR responding; 10 and 20 mg of diazepam decreased FR rates. FI rates were unaffected by d-amphetamine, with consistent increases occurring in only 1 of 4 subjects. Diazepam decreased FI rates. The number of reinforcers obtained in the FR and the FI was increased by d-amphetamine and decreased by diazepam for 2 of the 4 subjects and was unaffected by either drug in the other 2 subjects. Physiological measures, including heart rate and blood pressure and verbal reports of drug effects as measured by the Profile of Mood Scales and the Addiction Research Center Inventory were generally differentially affected by the 2 drugs. A multiple FR 30 FI 5 min schedule of point presentation may be capable of distinguishing behavioral effects of 2 different classes of drugs, the psychomotor stimulants and the minor tranquilizers. The results extend previously reported effects of diazepam on responding maintained under similar schedules from nonhuman subjects to humans. The effect of d-amphetamine in increasing rates of FR 30 responding was unexpected in that amphetamine is generally reported to produce decreases in the high rates of responding generated by FR schedules in nonhuman subjects.

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