title: Human brain dopamine metabolism in levodopa-induced dyskinesia and wearing-off.
abstract: The objective of this study was to identify dopamine (DA) metabolism pattern in Lewy body Parkinson's disease (PD) patients with dyskinesia (Dysk) only, with wearing-off (WO) only, or no motor complications (NMC) induced by levodopa (LD). DA, homovanillic acid (HVA), 3,4-dihydroxyphenylacetic acid (DOPAC), and 3-methoxytyramine (3-MT) were measured individual basal ganglia nuclei of nine PD patients who received LD for 6-18 years. Three patients had only Dysk, three only WO, and three had neither Dysk nor WO. Biochemical measurements in PD brains were compared with four non-neurological control brains from individuals matched for age and post-mortem retrieval time. DA levels in the PD were reduced in the caudate by 87% and putamen by 99%. In the caudates, the HVA/DA molar ratio as an index of DA metabolism was similar in the WO and the Dysk patients. However, in the putamen, the ratio of HVA/DA was significantly higher in the WO compared with the Dysk (p = 0.03)and the NMC (p = 0.04) groups of patients. In the putamen, the DOPAC levels were higher in the WO cases while in the Dysk cases, 3-MT levels were higher. The results suggest that in the WO only cases, the putaminal DA was in large measure metabolized intraneuronally while the DA metabolism in our Dysk only patients was mainly extraneuronal. We conclude that the magnitude and the site (intra vs. extraneuronal) of the synaptic DA metabolism in the putamen plays a significant role in LD-induced Dysk and WO.
authors.affiliation: Division of Neurology, University of Saskatchewan and Saskatoon Health Region, Rm 1663, Royal University Hospital, 103 Hospital Drive, Saskatoon, Saskatchewan, Canada S7N 0W8. ali.rajput@saskatoonhealthregion.ca
authors.forename: Ali H
authors.initials: AH
authors.lastname: Rajput
authors.forename: Mark E
authors.initials: ME
authors.lastname: Fenton
authors.forename: Thérèse
authors.initials: T
authors.lastname: Di Paolo
authors.forename: Harold
authors.initials: H
authors.lastname: Sitte
authors.forename: Christian
authors.initials: C
authors.lastname: Pifl
authors.forename: Oleh
authors.initials: O
authors.lastname: Hornykiewicz
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D001921:Brain / Q000187:drug effects / Q000378:metabolism*; D004298:Dopamine / Q000378:metabolism*; D004409:Dyskinesia, Drug-Induced / Q000378:metabolism*; D005260:Female; D006801:Humans; D007980:Levodopa / Q000009:adverse effects* / Q000494:pharmacology; D008297:Male
chemical_list: D007980:Levodopa; D004298:Dopamine