There are several dopaminergic pathways present in mammalian brain (Ungerstedt, 1971a, b, c, d; Schultz, 1982). Perhaps the most studied of these is the nigrostriatal pathway, which arises from pigmented cell bodies in the zona compacta of the substantia nigra and projects rostrally to the neostriatum (corpus striaturn). Parkinson’s disease is a syndrome of diverse etiology that is characterized by a degeneration of the above-mentioned nigrostriatal pathway. It has been estimated that the incidence of parkinsonism in the general population ranges from 100 to 150 cases per 100,000, with the prevalence being considerably greater in an older population sample (Schoenberg, 1987; Yahr, 1977). Biochemical and pathological characteristics of this disease include a greatly diminished neostriatal content of dopamine (DA) and its major metabolites and a marked loss of nerve cells in the zona compacta of the substantia nigra. Additional neuronal systems involved include noradrenergic and cholinergic systems.