Apomorphine as a preferential stimulant of self-inhibitory dopamine receptors in man.

In man, non emetic doses of apomorphine elicit a series of behavioural, neurological and psychological changes which are difficult to ascribe to the stimulation of postsynaptic dopamine receptors. Since similar effects are elicited by neuroleptic drugs, the functional changes induced by apomorphine in man might be interpreted as being the result of a decreased dopaminergic activity. The sedation and sleep, the improvement of choreic movements and the antipsychotic effect induced by non emetic doses of apomorphine are prevented by specific dopamine receptor blockers. These responses therefore are mediated through a stimulation of dopamine receptors leading to a decreased dopaminergic transmission. This new type of receptors might be identified with the so called "self-inhibitory" dopamine receptors.