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Effects of L-histidine depletion and L-tyrosine/L-phenylalanine depletion on sensory and motor processes in healthy volunteers.

ABSTRACT: BACKGROUND AND PURPOSE: Animal studies show that histamine plays a role in cognitive functioning and that histamine H3-receptor antagonists, which increase histaminergic function through presynaptic receptors, improve cognitive performance in models of clinical cognitive deficits. In order to test such new drugs in humans, a model for cognitive impairments induced by low histaminergic functions would be useful. Studies with histamine H1-receptor antagonists have shown limitations as a model. Here we evaluated whether depletion of L-histidine, the precursor of histamine, was effective in altering measures associated with histamine in humans and the behavioural and electrophysiological (event-related-potentials) effects. EXPERIMENTAL APPROACH: Seventeen healthy volunteers completed a three-way, double-blind, crossover study with L-histidine depletion, L-tyrosine/L-phenylalanine depletion (active control) and placebo as treatments. Interactions with task manipulations in a choice reaction time task were studied. Task demands were increased using visual stimulus degradation and increased response complexity. In addition, subjective and objective measures of sedation and critical tracking task performance were assessed. KEY RESULTS: Measures of sedation and critical tracking task performance were not affected by treatment. L-histidine depletion was effective and enlarged the effect of response complexity as measured with the response-locked lateralized readiness potential onset latency. CONCLUSIONS AND IMPLICATIONS: L-histidine depletion affected response- but not stimulus-related processes, in contrast to the effects of H1-receptor antagonists which were previously found to affect primarily stimulus-related processes. L-histidine depletion is promising as a model for histamine-based cognitive impairment. However, these effects need to be confirmed by further studies.

SUBMITTER: van Ruitenbeek P

PROVIDER: S-EPMC2697785 | biostudies-literature | 2009 May

REPOSITORIES: biostudies-literature

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Effects of L-histidine depletion and L-tyrosine/L-phenylalanine depletion on sensory and motor processes in healthy volunteers.

van Ruitenbeek P P Sambeth A A Vermeeren A A Young S N SN Riedel W J WJ

British journal of pharmacology 20090501 1

<h4>Background and purpose</h4>Animal studies show that histamine plays a role in cognitive functioning and that histamine H3-receptor antagonists, which increase histaminergic function through presynaptic receptors, improve cognitive performance in models of clinical cognitive deficits. In order to test such new drugs in humans, a model for cognitive impairments induced by low histaminergic functions would be useful. Studies with histamine H1-receptor antagonists have shown limitations as a mod ...[more]

PMID: 19413574

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Project description:Synthetic human ghrelin accelerates gastric emptying, reduces gastric accommodation, and results in numerical increases in postprandial symptom scores. The ghrelin receptor agonist, relamorelin, accelerates gastric emptying in patients with diabetic gastroparesis.To measure pharmacological effects of relamorelin on gastric accommodation, distal antral motility, and satiation in healthy volunteers.In a placebo-controlled, double-blind, randomized study of 16 healthy volunteers, we compared effects of 30 ?g subcutaneous (s.c.) relamorelin to placebo on: (i) gastric volumes measured by single photon emission computed tomography, (ii) 1-h postprandial distal antral motility index (MI) by 15-lumen perfusion gastroduodenal manometry, and (iii) satiation tested by Ensure nutrient drink test. Primary endpoints were: fasting and postprandial gastric volumes, distal antral phasic pressure activity (number of contractions, mean amplitude, and MI), and maximum tolerated volume. Results were normally distributed and the two treatment groups were compared using t-test.Relamorelin, 30 ?g s.c., significantly increased the number of contractions in the distal antrum during 0-60 min postmeal when compared to placebo (p = 0.022); this was also observed in the first two 15-min periods (p = 0.005 and 0.015 for number of contractions 0-15 and 16-30). There was borderline increase in MI0-15 (p = 0.055) and numerically increased MI0-60 (p = 0.139) and MI16-30 (p = 0.116). The amplitude of contractions was not significantly increased. Relamorelin did not significantly alter fasting or postprandial gastric volumes, gastric accommodation, or satiation volumes and symptoms.Relamorelin increases frequency of distal antral motility contractions without significant effects on amplitude of contractions. The lack of inhibition of accommodation and absence of increase in satiation symptoms support relamorelin for the treatment of symptomatic gastroparesis (ClinicalTrials.gov NCT02466711).

Dataset Information

Effects of L-histidine depletion and L-tyrosine/L-phenylalanine depletion on sensory and motor processes in healthy volunteers.

Publications

Effects of L-histidine depletion and L-tyrosine/L-phenylalanine depletion on sensory and motor processes in healthy volunteers.

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