Inclusion Criteria (all participants):
- Willingness to participate and written informed consent
- Aged 30 to 65 years at the time of screening
- Body mass index (BMI) ≤ 30
- Unremarkable neurological and physical examination
- Unremarkable standard blood parameter according to local reference values
Additional Inclusion Criteria for Restless Legs Syndrome (RLS) Patients:
- RLS according to current standard international criteria
- RLS symptoms ≥ 2 times per week for ≥ 1 year and during the past 12 months.
- Either current international RLS severity scale (IRLS) ≥ 15 or current IRLS ≥ 10 and RLS symptoms ≥ 4 times per week during the past 3 months.
Exclusion Criteria (all participants):
- Pregnancy, or breast feeding at time of screening.
- Recent anaesthesia (last 3 months).
- Sleep related breathing disorders during nocturnal polysomnography:
- Current history of psychiatric disorders according to the Diagnostic and Statistical Manual of Mental Disorders (DSM-IV).
- Life time history of any diagnosis of, medication or intervention for cardiovascular diseases.
- Current chronic treatment that may affect autonomic function.
- Any significant neurological disease or diagnosed metabolic diseases that may affect cardiovascular function and/or increase cardiovascular risk.
- Any unstable medical condition.
- Smoking > 5 cigarettes per day during the last 2 years.
- Work involving night shifts (22:00 - 06:00 h) during the past 2 years.
- Travel with > 6 time zone differences during the past 6 months.
- Participation in any other study involving investigational or marketed products concomitantly or within 3 months prior to the screening visit.
- Current participation in other clinical trials.
Additional Exclusion Criteria for RLS Patients
- Exposure to dopaminergic drugs > 12 months during life time and/or > 1 week during the past 3 months and/or current or during the past month.
- Exposure to other RLS relevant medication (such as opioids, antiepileptics, clonidine except hypnotics such as benzodiazepines) > 24 months during life time and/or > 1 week during the past 3 months and/or current intake.
- Intake of hypnotics (such as benzodiazepines) during the past month.
- Other significant sleep disorder except symptoms potentially related to RLS such as insomnia and daytime sleepiness.
- Any contraindication or known hypersensitivity to dopaminergic drugs.
Additional Exclusion Criteria for Control Subjects
- Any pharmacological treatment that may affect sleep and/or sleep related movement disorders during the last 3 months.
- Any clinically significant sleep disorders according to the International Classification of Sleep Disorders (ICSD)12.
- Increased daytime sleepiness as indicated by an Epworth Sleepiness Scale (ESS) score > 11.