Increase in salsolinol level in the cerebrospinal fluid of parkinsonian patients is related to dementia: advantage of a new high-performance liquid chromatography methodology

The study was carried out on the lumbar cerebrospinal fluid (CSF) samples taken from nonparkinsonian, early parkinsonian, and advanced parkinsonian patients. Some patients showed dementia, and some were treated with L-dopa. In the samples, salsolinol (1-methyl-6,7-dihydroxy-1,2,3,4-tetrahydroisoquinoline) was assayed with a newly developed sensitive high-performance liquid chromatography (HPLC) method; 3-O-methyldopa (3-O-MD) and homovanillic acid (HVA) were also assayed by HPLC. CSF salsolinol concentrations were significantly enhanced in patients with signs of dementia, regardless of the degree of parkinsonism, and were not affected by L-dopa treatment; HVA and, particularly, 3-O-MD levels were elevated in patients receiving L-dopa. The strong association of CSF salsolinol level with dementia, but not with L-dopa treatment suggests that salsolinol does not originate from L-dopa metabolism, and that its elevation is an indicator of neurodegenerative processes resulting in damage to brain areas mediating cognitive functions. We found no correlation between the advancement of parkinsonism and the concentrations of 3-O-MD and HVA.