Tryptophan hydroxylase activity in the brains of controls and parkinsonian patients

The activity of tryptophan hydroxylase was measured in nine regions of human brains from controls and patients with Parkinson's disease, striatonigral degeneration, Shy-Drager syndrome and progressive supranuclear palsy by high performance liquid chromatography with fluorescence detection. The regional distribution of the enzyme activity in control brains was similar to that of serotonergic neurons; relatively high activity was found in the raphe nucleus, locus coeruleus and substantia nigra. The activity in the thalamus in Parkinson's disease and that in the locus coeruleus, raphe nucleus and substantia nigra in striato-nigral degeneration were significantly lower than that of controls (p less than 0.05). In most other brain regions in parkinsonian patients the activity was relatively lower than that of controls except the caudate nucleus and nucleus accumbens where the activity was relatively higher than that of controls. Marked decrease in the enzyme activity in various brain regions was observed in striato-nigral degeneration, Shy-Drager syndrome, and progressive supranuclear palsy. These results suggest that the activity of tryptophan hydroxylase in serotonergic neurons is reduced in the brains of parkinsonian patients and of patients with degenerative nervous diseases.