Norepinephrine, 3-methoxy 4-hydroxyphenylethyleneglycol and homovanillic acid levels were similar in the locus ceruleus of 13 controls and 8 parkinsonian patients with no intellectual deterioration, but were decreased in 7 demented patients. The concentration of dopamine was similarly diminished in non-demented and demented parkinsonians, and binding of 3H-desmethylimipramine and 3H-rauwolscine was not abnormal in parkinsonians. These data indicate that norepinephrine metabolism in the locus ceruleus is subnormal only in demented parkinsonians.

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The density of high-affinity 3H-imipramine and 3H-paroxetine binding sites (two serotonin-uptake blockers) was decreased in the putamen of parkinsonian patients. The correlation between serotonin levels and the number of 3H-imipramine and 3H-paroxetine binding sites suggests that they are located on serotoninergic nerve terminals and could be used to study serotoninergic innervation in the human brain. Since imipramine and paroxetine are powerful antidepressants, these results furthermore suggest that decreased serotoninergic transmission may be implicated in the pathophysiology of depression in Parkinson's disease.