Abstract

d-Amphetamine, cocaine and pipradrol increased the locomotor activity of groups of five mice. Although both cocaine and pipradrol caused greater increases in locomotor activity than those attained with d-amphetamine, only d-amphetamine caused significant changes in brain norepinephrine, dopamine or 5-HT levels at doses which increased locomotor activity. These results indicate that changes in brain amines caused by d-amphetamine are neither secondary to the activity-increasing effects of d-amphetamine nor result from a nonspecific action of drugs which increase locomotor activity. Changes in locomotor activity caused by d-amphetamine were not correlated closely with changes in the brain content of norepinephrine, dopamine or 5-HT. Small doses of d-amphetamine increased brain dopamine levels. Larger doses decreased the brain content of norepinephrine and increased the brain content of 5-HT. Pretreatment of mice with either iproniazid or reserpine enhanced the activity-increasing effect of d-amphetamine.