The effect of lithium on amphetamine-induced locomotor stimulation.

A behavioural study was performed to investigate how lithium interacts with monoamine mechanisms. Acute lithium pretreatment partially antagonized amphetamine-induced locomotor stimulation in mice. A rather small dose of L-dopa, which had no stimulant effect on locomotor activity of its own, caused a dose-dependent antagonism of the lithium-induced suppression of the amphetamine-induced locomotor stimulation. Additionally, acute lithium pretreatment had no effect on the apomorphine-clonidine-induced locomotor stimulation after elimination of presynaptic activity by means of pretreatment with reserpine and alpha-MT. Our interpretation of these results is that the inhibitory effect on amphetamine-induced locomotor stimulation is likely to be mediated via presynaptic mechanisms (i.e., decreased release of catecholamines or inhibition of catecholamine synthesis or a combination of both mechanisms) and, further, lithium seems to have no effect at or beyond the catecholamine receptors. However, the possibility that lithium may increase the activity in neuronal systems antagonizing the catecholamine neurons cannot be excluded.