DETERMINATION OF 5-HYDROXYTRYPTAMINE AND TRYPTOPHAN BY LIQUID-CHROMATOGRAPHY IN WHOLE-BLOOD - ITS INTEREST FOR THE EXPLORATION OF MENTAL-DISORDERS

Aymard Nicole, Prisca Honore and Isabelle Carbuccia : Determination of 5-hydroxytryptamine and tryptophan by Liquid chromatography in whole blood. Its interest for the exploration of mental disorders. Frog. Neuro-Psychopharmacol. & Biol. Psychiat 1994, 18(1): 77-86. 1. 5-Hydroxytryptamine (5-HT) is a well known neurotransmitter implicated in mental disorders, tryptophan (Trp) as amino acid precursor may be interesting. 2. A rapid and simple reversed-phase (mu Bondapac C18 as stationary phase) liquid chromatographic method with fluorimetric detection (excitation : 302 nm, emission : 340 nm) is described for the quantitation of 5-hydroxytryptamine (5-HT) and fr ee tryptophan (Trp), in whole blood. 5-fluoro-dl-tryptophan (5-FdlT) was used as internal standard. The mobile phase was 0,01 M phosphate buffer (pH = 4,5) with 0,0025 M 1-heptane sulfonic acid and 15 % methanol. 3. In blood of healthy subjects (n = 30), the concentrations were, for 5-HT : 258 +/- 68 ng/ml and for Trp : 5,7 +/- 1,02 mu g/ml. 4. The assay was used to follow the effect of antidepressant drugs, as a 5-HT reuptake inhibitor (clomipramine) and a monoamine oxidase inhibitor (moclobemide). After 4 week treatments. we observed, with clomipramine by 7 patients (150 mg/day) a highly significant reduction (p < 0,01) in 5-HT levels (77 % +/- 12) and with moclobemide by 8 patients (300 or 450 or 600 mg/day) a highly significant increase in 5-HT levels (from 16 %, to 300 % according to the drug dosage). These two drugs did not influence blood Trp concentrations. 5. Assays on whole blood present various advantages : (i) the simplicity for clinical departments (ii) the absence of sample pretreatment and (iii) the assurance that the entire platelet population is assayed since all of the 5 HT in blood is bound to platelets.