Dopamine autoreceptor stimulation: Clinical significance

Recent studies of the effects of low doses of dopamine agonists, designed to stimulate dopamine autoreceptors and hence diminish the synthesis and release of dopamine, were based on a series of basic research studies which demonstrated the existence of autoreceptors on dopamine neurones of the nigrostriatal, mesolimbic and mesocortical dopaminergic neurones. Evidence for autoreceptors on the tuberoinfundibular dopamine neurones which participate in the regulation of prolactin and growth hormone secretion is lacking. Some recent reports have questioned the existence of dopamine autoreceptors on the mesolimbic and nigrostriatal dopamine neurones. Specificity of various dopamine agonists and antagonists for the dopamine autoreceptor will be reviewed. The sedative, anxiolytic, antipsychotic, antidyskinetic and neuroendocrine effects of low dose dopamine agonists in man will be described. Low dose apomorphine, N-propylapomorphine and bromocriptine have been reported to have antipsychotic effects in the major psychoses, to diminish tardive dyskinesia and to enhance extrapiramidal insufficiency. A unique depressive state which developed in a small proportion of psychiatric patients after low dose apomorphine will be described. Further evidence for the lack of dopamine autoreceptors on the tuberoinfundibular dopamine neurones in man will be presented. Strategies for further study of the dopamine autoreceptor concept in man will be discussed.