Dopamine agonists in Parkinson's disease.

The main pathologic hallmark of Parkinson's disease is a degeneration of the dopaminergic cells in the substantia nigra, pars compacta and--to a lesser extent--in the ventral tegmental area. Striatal dopamine concentrations are significantly reduced before clinical symptoms become apparent. Recent neuroanatomic and function studies have revealed that the nigrostriatal dopaminergic projection is only one of the neuronal elements integrated into extensive basal ganglia-thalamocortical circuits that are intimately involved in the regulation of motor activity. The possibilities for therapeutic intervention at the level of the different dopamine receptor subtypes and their effect on the regulation of motor behavior will be briefly reviewed. Dopamine precursors are considered to provide the best symptomatic treatment, whereas dopamine agonists, although less effective, might be important in slowing the progression of the disease. Our results with pergolide as monotherapy and in combination therapy in patients with Parkinson's disease also are discussed.