Sprague-Dawley rats (150-200 g), serving as their own controls, were evaluated for hyperactivity (HyA) and stereotyped behavior (SB) produced by chronic (1 wk) i.p. administration of different doses of drugs that have differential NE [norepinephrine] and DA [dopamine] agonist properties. Drugs utilized were d- and l-amphetamine, metamphetamine, cocaine and the specific and direct DA receptor agonist apomorphine. This was followed by 1 wk of rest after which all rats received 3 wk of Li s.c. In the last week of Li administration, each rat was given the same drug administered previously at the same dose. In all cases, Li decreased HyA and SB, suggesting Li effects at the pre- and postsynaptic neuron (receptor).