Effects of d-amphetamine and caffeine in humans under a cocaine discrimination procedure

Behav Pharmacol. 1998 May;9(3):207-17.


This study examined further the pharmacological specificity of an oral cocaine discriminative stimulus in humans. Five male cocaine-abusing volunteers (two African-American/three Caucasian) were trained to discriminate between a low dose of cocaine hydrochloride (80 mg/70 kg, p.o.) and placebo. Once the criterion for discrimination was met (i.e. > or = 80% correct responding for four consecutive sessions), dose-effect curves were determined for the dopamine reuptake inhibitor cocaine (20, 40, 80, 120 mg/70 kg, p.o.), the indirect dopamine agonist d-amphetamine (5, 10, 20 mg/70 kg, p.o.) and the adenosine antagonist caffeine (150, 300, 600 mg/70 kg, p.o.). Cocaine, d-amphetamine and caffeine each produced dose-related increases in cocaine-appropriate responding. Each compound produced at least a trend towards increases in a few stimulant-like self-reports and vital signs. When the relationship between cocaine-appropriate responding and self-reports were examined, cocaine and d-amphetamine, but not caffeine, had a similar profile of significant associations between discriminative performance and stimulant-like self-reports. These results suggest that, although the cocaine discriminative stimulus (80 mg/70 kg) is not specific only to stimulants with primarily dopaminergic actions, its pharmacological specificity may be more clearly defined when the relationship between discrimination and self-reports is examined.

Publication types

  • Clinical Trial
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Adult
  • Caffeine / pharmacology*
  • Central Nervous System Stimulants / pharmacology*
  • Cocaine / pharmacology*
  • Dextroamphetamine / pharmacology*
  • Discrimination Learning / drug effects
  • Discrimination, Psychological / drug effects*
  • Dopamine Uptake Inhibitors / pharmacology*
  • Female
  • Generalization, Stimulus
  • Hemodynamics / drug effects
  • Humans
  • Male
  • Middle Aged
  • Psychomotor Performance / drug effects


  • Central Nervous System Stimulants
  • Dopamine Uptake Inhibitors
  • Caffeine
  • Cocaine
  • Dextroamphetamine