Effect of L-threo-3,4-dihydroxyphenylserine chronic administration on cerebrospinal fluid and plasma free 3-methoxy-4-hydroxy-phenylglycol concentration in patients with Parkinson's disease.

L-Threo-3,4-dihydroxyphenylserine (L-threo-DOPS) was administered as a means of treating akinesia in 9 patients with Parkinson's disease and one with pure akinesia. Akinetic symptoms were improved in 7 of 10 patients. During chronic L-threo-DOPS treatment, cerebrospinal fluid (CSF) and plasma concentrations of free 3-methoxy-4-hydroxyphenylglycol (MHPG) and L-threo-DOPS were measured in these 10 patients. The results show that there were no significant changes in either CSF or plasma free MHPG concentrations before or during L-threo-DOPS administration. The L-threo-DOPS concentration during treatment was not measurable in the CSF of 2 patients nor in the plasma of 1 out of 4 patients given only L-threo-DOPS. It was, however, measured in all patients treated with a combination of L-threo-DOPS and L-DOPA plus carbidopa. The results show that L-threo-DOPS is transported into the CSF, and suggest that its active mechanism may be further clarified by studying its action on not only noradrenaline, but also other neurotransmitters.