In Vivo Evidence for Differential Association of Striatal Dopamine and Midbrain Serotonin Systems With Neuropsychiatric Symptoms in Parkinson's Disease

Parkinson's disease affects various neurotransmitter systems. Using SPECT, the authors measured [¹²³I]β-CIT binding ratios of the caudate, putamen, medial thalamus, and dorsal midbrain over cerebellum in 16 patients with Parkinson's disease, and examined correlations with clinical ratings. Whereas striatal binding ratios (reflecting regional dopamine transporter densities) were associated with motor symptoms, dorsal midbrain binding ratios (reflecting regional serotonin transporter densities) were significantly correlated with the mentation, behavior, and mood subscale of the Unified Parkinson's Disease Rating Scale. These findings indicate that degeneration of the nigrostriatal dopaminergic neurons and a dysfunctional serotonergic raphe system contribute differentially to motor deficits and neuropsychiatric symptoms in Parkinson's disease.