Effects of Training Dose on the Relationship Between Discriminative-Stimulus and Self-Reported Drug Effects of d-Amphetamine in Humans

Abstract

64(2) 319–326, 1999.—The aim of the present experiment was to examine the relationship between the discriminative-stimulus and self-reported effects of drugs in humans. To accomplish this aim, nine healthy adult volunteers (four females, five males) were trained to discriminate between placebo and 10 mg d-amphetamine (low-dose group) or 20 mg d-amphetamine (high-dose group). After acquiring the placebo-amphetamine discrimination, a range of doses of d-amphetamine (1.25–20 mg) was tested to determine if they shared discriminative stimulus effects with the training dose. Participants in the low-dose group exhibited a significant leftward shift in the dose–response function for discrimination performance, which is concordant with previous preclinical and human drug discrimination studies that assessed the effects of training dose. Consistent with the drug discrimination findings, participants in the low-dose group exhibited a significant leftward shift in the dose–response function for several self-reported drug effects (e.g., Like the Drug and Stimulated). However, several other self-reported drug effect items were not significantly influenced by training condition (e.g., Anxious/Nervous and Bad Effects). These results suggest that the discriminative-stimulus and self-reported drug effects of d-amphetamine overlap, but are not isomorphic. Furthermore, these results illustrate that behavioral history significantly influences subsequent drug effects in humans.