Dissociated effects of amphetamine on arousal and cortical blood flow in humans

The effects of intravenous amphetamine infusion (0.3 mg/kg) on cerebral blood flow (CBF) and measures of autonomic and behavioral arousal were studied in 12 normal male volunteers in a placebo-controlled crossover design. Nonsignificant decreases were seen in CBF (measured by 133Xe inhalation), despite significant increases in autonomic and behavioral arousal. The apparent dissociation of CBF and arousal appears to be compatible with other human experiments suggesting that amphetamine decreases CBF and metabolism, as well as with neurobiological findings on the effects of catecholamines on resting cortical activity and mechanisms of increased attention. The results differ substantially, however, from findings of increased CBF and metabolism in animals. Although the larger doses used in animals most likely explain the discrepancy, technical limitations in human brain imaging cannot be excluded.