Effect of a synthetic norepinephrine precursor, L-threo-3,4- dihydroxyphenylserine on the total norepinephrine concentration in the cerebrospinal fluid of parkinsonian patients.

We studied the effect of a synthetic norepinephrine precursor, L-threo-3,4-dihydroxyphenylserine (L-threo-DOPS) on the total (conjugated and unconjugated) norepinephrine concentrations in the cerebrospinal fluid (CSF) of 6 parkinsonian patients with freezing phenomenon. The total norepinephrine concentrations in the CSF increased from 5- to 75-fold after treatment with L-threo-DOPS. The degree of increase in the norepinephrine (NE) concentrations was closely correlated to the dosage of L-threo-DOPS. The freezing phenomenon improved in 3 out of 6 patients.