The use of free tryptophan and prolactin as peripheral indices of brain serotoninergic activity
type: CreativeWork
description: The central fatigue hypothesis suggests that during prolonged exercise, the increased plasma free-tryptophan (f-Trp) concentration may lead to an increased rate of synthesis of brain serotonin (5-HT). This may impair central nervous system function and cause increased perceptions of fatigue and deteriorate exercise performance. Two-fold increases in plasma concentrations of f-Trp have resulted in a 20% and 53% increase in brain Trp and forebrain Trp respectively. In addition, it has been suggested that 5-HT is involved in the stimulation of PRL release. The aim of the present thesis was to examine the relationship between the main peripheral markers of central fatigue, namely venous concentrations of f-Trp and prolactin (PRL), under three different experimental conditions. It was hypothesised that the changes in venous concentrations of f-Trp and PRL would exhibit similar patterns. Plasma f-Trp concentration increased by 110% after 2 h of cycling in normobaric hypoxia at a workload corresponding to 55% of VO2max determined in normobaric normoxia (P < 0.05). Serum PRL concentration did not differ between trials but the mean concentration increased at 30 min post exercise (P < 0.05). Following high intensity exercise for 30 s, plasma f-Trp concentration decreased by 23.5% (P < 0.05), whereas serum PRL concentration did not change (P > 0.05). Oral administration of L-Trp was followed by an increased plasma f-Trp concentration of 920%, however, plasma PRL concentrations decreased by 32.6% at the same time-point (P < 0.05). Analysis of functional magnetic resonance imaging of the brain demonstrated a different pattern of brain activation while subjects performed the interference task of the counting Stroop test following L-Trp ingestion. From these results it can be proposed that central fatigue is likely not to play any part during high-intensity exercise lasting 30s. However, the 110% and 920% increase in plasma f-Trp concentration during prolonged exercise in normobar…
abstract: The central fatigue hypothesis suggests that during prolonged exercise, the increased plasma free-tryptophan (f-Trp) concentration may lead to an increased rate of synthesis of brain serotonin (5-HT). This may impair central nervous system function and cause increased perceptions of fatigue and deteriorate exercise performance. Two-fold increases in plasma concentrations of f-Trp have resulted in a 20% and 53% increase in brain Trp and forebrain Trp respectively. In addition, it has been suggested that 5-HT is involved in the stimulation of PRL release. The aim of the present thesis was to examine the relationship between the main peripheral markers of central fatigue, namely venous concentrations of f-Trp and prolactin (PRL), under three different experimental conditions. It was hypothesised that the changes in venous concentrations of f-Trp and PRL would exhibit similar patterns. Plasma f-Trp concentration increased by 110% after 2 h of cycling in normobaric hypoxia at a workload corresponding to 55% of VO2max determined in normobaric normoxia (P < 0.05). Serum PRL concentration did not differ between trials but the mean concentration increased at 30 min post exercise (P < 0.05). Following high intensity exercise for 30 s, plasma f-Trp concentration decreased by 23.5% (P < 0.05), whereas serum PRL concentration did not change (P > 0.05). Oral administration of L-Trp was followed by an increased plasma f-Trp concentration of 920%, however, plasma PRL concentrations decreased by 32.6% at the same time-point (P < 0.05). Analysis of functional magnetic resonance imaging of the brain demonstrated a different pattern of brain activation while subjects performed the interference task of the counting Stroop test following L-Trp ingestion. From these results it can be proposed that central fatigue is likely not to play any part during high-intensity exercise lasting 30s. However, the 110% and 920% increase in plasma f-Trp concentration during prolonged exercise in normobar…
author: Morgan, Rhian
language: eng
keywords: Serotoninergic mechanisms
date published: 2002-12
date modified: 2026-07-24T04:38:53Z
provider: University of South Wales
publisher: Networked Digital Library of Theses and Dissertations
type: WebPage
source organization: University of South Wales