Physiological Assessment of the Endothelium - Circadian Rhythm and Role of the Sympathetic Nervous System

Study Overview
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Brief Summary
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The purpose of this study is to determine whether interventions aimed at increasing sympathetic tone modify endothelial function measures as assessed by the measurement of flow-mediated dilation (FMD) and constriction (FMC). The investigators hypothesize that the three interventions under study will increase FMC while causing a blunting in FMD. Further, the investigators plan to study the circadian variability of FMC and FMD. The investigators hypothesize a peak of FMD in the late hours of the day and a peak of FMC in the early hours.

Official Title
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Studies on the Physiological Meaning of Flow-mediated Constriction, Flow-mediated Dilatation and Vasomotion/Flowmotion: Circadian Variability and Role of the Sympathetic Nervous System.

Conditions
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Endothelial Function

Intervention / Treatment
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* Procedure: Mental stress
* Other: no intervention
* Procedure: Myogenic activation
* Procedure: Cold pressure test


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: healthy volunteers with no cardiovascular risk factor, no current disease, normal laboratory parameters and ECG. Exclusion Criteria: any active disease

Ages Eligible for Study
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Minimum Age: 18 Years
Maximum Age: 40 Years

Sexes Eligible for Study
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Male

Accepts Healthy Volunteers
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Accepts Healthy Volunteers

Study Plan
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How is the study designed?
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Design Details

Primary Purpose: Basic Science
Allocation: Randomized
Intervention Model: Crossover Assignment
Masking: None (Open Label)


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Active Comparator: Myogenic activation<br>Subjects will undergo endothelial function assessment at rest and, after a 45 minutes pause, 1 minute after begin of myogenic activation | Procedure: Myogenic activation<br>* A pneumatic cuff will be inflated to suprasystolic pressure around both thighs and the subjects will be asked to perform plantar flexion exercises.<br>|
| Active Comparator: Cold pressure test<br>Subjects will undergo endothelial function assessment at rest and, after a 45 minutes pause, 1 minute after begin of cold pressure test | Procedure: Cold pressure test<br>* A hand will be placed in ice-cold water.<br>|
| Active Comparator: mental stress<br>Subjects will undergo endothelial function assessment at rest and, after a 45 minutes pause, 1 minute after begin of mental stress | Procedure: Mental stress<br>* Subjects will be asked to perform complex mathematic operations at a very fast pace<br>|
| Active Comparator: Control<br>Control visit - no intervention performed - subjects will undergo endothelial function measurement twice at a distance of 45 minutes | Other: no intervention<br>* control visit<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Change in FMD in response to sympathetic activation | Flow-mediated dilation will be measured at rest and during each of the interventions. | Change in FMD before versus 1 Minute after begin of intervention | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Change in FMC during sympathetic activation | Change in Flow-mediated constriction induced by each of the interventions. | Change in FMC before versus 1 minute after begin of each intervention | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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endothelial function, sympathetic nervous system