Effect of d-amphetamine on prepulse inhibition of the startle reflex in humans

Prepulse inhibition of the startle reflex (PPI) is attenuated in animals after administration of d-amphetamine and other drugs that stimulate mesolimbic dopamine activity. The aim of the present study was to evaluate the effects of d-amphetamine (20 mg) on a variety of psychophysiological and subjective measures, including PPI, in humans. Thirty-six participants (18 women) participated in a double-blind, placebo controlled, repeated measures study. In one session, participants received d-amphetamine (20 mg) orally, and in the other session, participants received an identical appearing placebo. Participants were assessed at 60, 90, and 120 min after ingestion with a 5-min block of startle trials (six control trials and six prepulse trials) followed by subjective measures of stimulation and mood. d-Amphetamine increased subjective measures of stimulation and euphoria, attenuated PPI, and increased heart rate, relative to placebo treatment. The effect of d-amphetamine on the subjective measures was substantial and consistent over time, while the effect on PPI was only observed at 90 min after ingestion, and the effect on heart rate was limited to 90 and 120 min after ingestion.