Degree of Selectivity of Pergolide as an Agonist at Presynaptic Versus Postsynaptic Dopamine Receptors

Abstract

Pergolide mesylate is a potent dopamine agonist that is being evaluated clinically in Parkinson disease, hyperprolactinemia, and other diseases. Pergolide activates both presynaptic and postsynaptic dopamine receptors, with some apparent selectivity for the presynaptic dopamine autoreceptors. In rats, low doses of pergolide (0.01 mg/kg or less, intraperitoneally) decreased dopamine turnover in brain, decreased serum prolactin concentration, and reduced blood pressure in spontaneously hypertensive rats. At somewhat higher doses (0.05 mg/kg or more, intraperitoneally), pergolide caused contralateral turning in nigrostriatal-lesioned rats, elevation of serum corticosterone, and hypermotility with stereotyped behavior. All of these actions are thought to be due to stimulation of dopamine receptors at various sites, but the data suggest that pergolide may have preferential affinity for presynaptic dopamine receptors. If low doses of pergolide can reduce dopaminergic transmission by activating presynaptic receptors that control dopamine release, then this action might be therapeutically useful in treating schizophrenia without causing tardive dyskinesia or in the treatment of tardive dyskinesia. The long duration of action of pergolide seen in animal and human studies could be an important advantage over some other dopamine agonists such as apomorphine.