Stress, Psychological
Conditions
Keywords
L-tyrosine
Brief summary
L-tyrosine is a chemical precursor of dopamine. Under specific conditions, tyrosine administration can increase brain dopamine levels and therefore several studies have explored whether tyrosine supplementation can have a beneficial effect on cognitive and behavioural performance that is dependent on dopaminergic function. However, the effects of tyrosine supplementation are mixed: some studies show positive effects while others do not. Stress leads to an increase in dopaminergic activity and turnover in the brain, resulting in a decrease in brain dopamine levels. We propose to study the contribution of tyrosine to decision making and more particularly to the processes of response selection (mediated by the prefrontal cortex and under the influence of the dopaminergic system) in stressful situations.
Interventions
BIOLOGICALBlood collection
A blood sample will be collected before and after treatment administration
The participants will be administered 4 capsules of L-Tyrosine 500 mg per oral route
DRUGPlacebo
The participants will be administered 4 capsules of Lactose 500 mg (placebo) per oral route
BEHAVIORALCognitive tasks
The participants will perform cognitive decision-making tasks: Simon task and masking task after treatment administration
OTHERStress exposure
Unpleasant but not painful skin stimulations will be administered to the participants at variable intervals on the left leg during the cognitive tasks
BEHAVIORALAnxiety scale
Spielberger's State Trait Anxiety Inventory (STAI) will be filled by the participants before and after cognitive tasks
DEVICEElectromyography (EMG)
Electromyography measurements will be performed during cognitive tasks.
DEVICEElectroencephalography (EEG)
Electroencephalography measurements will be performed during cognitive tasks.
Sponsors
Direction Centrale du Service de Santé des Armées
Study design
Allocation
RANDOMIZED
Intervention model
CROSSOVER
Primary purpose
PREVENTION
Masking
TRIPLE (Subject, Investigator, Outcomes Assessor)
Masking description
The pharmacist, carrying out the packaging and labelling of the treatment units, will ensure the blinding. Neither the participant nor the investigator will know what treatment is being administered.
Intervention model description
The study is composed of 4 arms: 1. Tyrosine treatment without stress exposure 2. Tyrosine treatment with stress exposure 3. Placebo treatment without stress exposure 4. Placebo treatment with stress exposure Every participants will participate in the 4 arms in a random order.
Eligibility
Sex/Gender
ALL
Age
18 Years to 65 Years
Healthy volunteers
Yes
Inclusion criteria
* From 18 to 65 years of age
Exclusion criteria
* Tyrosine intake within the previous 15 days * History of neurological or psychiatric disorder * History of nephrological or endocrine disorder or liver failure * Hereditary tyrosinemia
Design outcomes
Primary
| Measure | Time frame | Description |
|---|---|---|
| Reaction Time | At day 9 (9 days after enrollment) | Reaction Time at the cognitive tasks |
| Number of incorrect responses | At day 9 | Number of incorrect responses at the cognitive tasks |
Secondary
| Measure | Time frame | Description |
|---|---|---|
| Error negativity | At day 9 | Error negativity on motor evoked potentials (measured by EMG) |
| Correlation coefficient between anxiety level and tyrosinemia | At day 9 | Correlation coefficient between anxiety level (measured by anxiety scale) and tyrosinemia (measured in blood sample) |
| Correlation coefficient between anxiety level and plasma tyrosine | At day 9 | Correlation coefficient between anxiety level (measured by anxiety scale) and plasma tyrosine (measured in blood sample) |
| Correlation coefficient between cortisolaemia and melatoninaemia | At day 9 | Correlation coefficient between cortisolaemia and melatoninaemia (measured in blood sample) |
Countries
France
Outcome results
None listed