Psychophysical profiles differentiate drugs of abuse.

Behavioral reaction times and both auditory and visual absolute thresholds were determined in baboons before and after the administration of stimulant and depressant drugs of abuse. Pentobarbital and diazepam increased reaction times and elevated the visual threshold in a dose-dependent manner. Diazepam also raised the auditory threshold though pentobarbital did not. Chlordiazepoxide affected neither sensory thresholds nor reaction times over the same dose range; d-methylamphetamine elevated the visual threshold, but did not elevate the auditory threshold or increase reaction times.