Simultaneous determination of four monoamine metabolites and serotonin in cerebrospinal fluid by "high-performance" liquid chromatography with electrochemical detection; application for patients with Alzheimer's disease.

Abstract

We describe an optimized, sensitive assay procedure for simultaneously determining 3-methoxy-4-hydroxyphenylglycol, 3,4-dihydroxyphenylacetic acid, and serotonin in human lumbar cerebrospinal fluid. The assay is based on liquid chromatography with an electrochemical detection system equipped with a newly developed, highly sensitive graphite electrode. Before assay, samples are deproteinized with perchloric acid, 0.2 mol/L. The within- and between-day CVs were less than 2.5% and 6.7%, respectively, for all compounds. The lower limits of detection for 3-methoxy-4-hydroxyphenylglycol and 3,4-dihydroxyphenylacetic acid were 0.5 pg and for the other three analytes 1.5 pg per injection. Preliminary data on monoaminergic metabolites by the current assay showed that concentrations of dopaminergic and serotonergic metabolites were significantly (P less than 0.05) lower in patients with Alzheimer's disease than in the age-matched controls. In addition, the concentration of 3,4-dihydroxyphenylacetic acid correlated significantly (P less than 0.01) with that of homovanillic acid, suggesting that monitoring either of these metabolites in cerebrospinal fluid can be used as an index of central dopaminergic activity.

Cerebrospinal Fluid Markers of Alzheimer's Disease

“…Interpretation of this finding is difficult because it has not been reproduced by other groups as yet. The same holds true for reports on reduction of dopamine‐β‐hydroxylase activity in CSF of AD patients 42–56 …”

“…SLI in CSF does not merely reflect hypothalamic function. Lack of a rostro‐caudal SLI gradient in CSF, as well as the presence of a blood‐CSF barrier for somatostatin, and the good correlation between SLI in brain biopsies and CSF in two AD patients, are all consistent with the notion that changes in CSF SLI reflect alterations in somatostatin secretion of the cerebral cortex 28–59 . All studies on SLI in CSF of AD patients report a reduction of approximately 40% as compared to control populations, which differed among studies 21 , 26 , 28 , 30 , 60–67 .…”

“…The above‐mentioned factors may explain some of the conflicting findings discussed hereafter. Nevertheless, HVA concentration in CSF has frequently been found to be decreased by approximately 30%–60% in lumbar CSF of AD patients, 15 , 38–45 although this could not be reproduced in all studies performed 21 , 33 , 46–48 . Kaye et al 49 found reductions of HVA and biopterin, a co‐factor of tyrosine hydroxylase in CSF to be significant in AD patients with extrapyramidal features only.…”

“…HIAA levels in CSF appear to be of little value in the diagnosis of AD. Reductions ranging from 15% to 40% 38 , 39 , 43–45 , 52 as well as an increase of 85% 53 have been reported, whereas various studies found no differences between AD and control populations 21 , 40 , 41 , 48 , 49 , 51 , 54 . Measurements in CSF of serotonin itself rather than its metabolite HIAA, are variable, depending on the methods used, as shown by Vollicer et al 52 , 54 …”

“…Zubenko et al 33 even found an increase of HVA in CSF from patients with only a mild degree of dementia. Increased HVA may result from an increased conversion of DOPAC to HVA, as suggested by reduced DOPAC concentrations in CSF of demented patients 33–45 …”