title: Tryptophan depletion selectively reduces CSF 5-HT metabolites in healthy young men: results from single lumbar puncture sampling technique.
abstract: Plasma tryptophan (Trp) depletion is a commonly used tool for determining the role of brain serotonin (5-HT) function in a variety of psychiatric disorders. This study measured the cerebrospinal fluid (CSF) monoamine metabolite response to Trp depletion and control testing in five healthy subjects utilizing a single lumbar puncture. Testing was done in a placebo-controlled, double-blind, randomized, cross-over design. Plasma-free and total Trp levels and behavioural ratings were obtained prior to and 5 h after ingestion of each amino-acid drink. CSF was obtained by performing a standard lumbar puncture 7 h after ingestion of the drink. Compared to control testing, Trp depletion caused a significant decrease of CSF 5-hydroxyindoleacetic acid (5-HIAA) (p = 0.03), but not of homovanillic acid or 3-methoxy-4-hydroxy-phenylglycol. Behavioural ratings were minimally affected in all subjects. This confirms that plasma Trp depletion reduces central nervous system measures of 5-HT function and suggests that the single lumbar puncture technique may be sufficient to detect the extent of CSF 5-HIAA changes during Trp depletion studies.
authors.forename: Francisco A.
authors.initials: FA
authors.lastname: Moreno
authors.forename: Cameron
authors.initials: C
authors.lastname: McGavin
authors.forename: T. Phillip
authors.initials: TP
authors.lastname: Malan
authors.forename: Alan J.
authors.initials: AJ
authors.lastname: Gelenberg
authors.forename: George R.
authors.initials: GR
authors.lastname: Heninger
authors.forename: Aleksander A.
authors.initials: AA
authors.lastname: Mathé
authors.forename: Pedro L.
authors.initials: PL
authors.lastname: Delgado