Deciphering the Mechanisms of Central BP Regulation in Patients With PD Associated With Orthostatic Hypotension

Phase 1: Inclusion Criteria: * Signed informed consent * Age ≥ 18 years and \<75 years * Normal office blood pressure (\<140/90 mmHg) * For women of childbearing potential: using or willing to use during the study a reliable contraception method compatible with MRI Exclusion Criteria: * Schellong test showing OH (drop of Systolic BP \>20 mmHg or Diastolic BP \>10 mmHg) * Pregnant or lactating women * Refusal to be informed of incidental findings * Any medication (acute or chronic prescription) except oral contraception * Clinical significant abnormal blood test as assessed by the investigator * Chronic or acute illness * Concomitant participation in a clinical trial * Blood donation in the 60 previous days * Contra-indications for MRI * Unable to follow study procedures * Having a hierarchical relationship with the investigator or being family of the investigator Phase 2: Inclusion Criteria: * Signed informed consent * Fulfilling Movement Disorder Society clinical criteria for "clinically established PD" * Age ≥18 years and \<75 years * PD treated by dopamine replacement therapy (DRT) * Willing and able to comply with the visit schedule and study procedures * Autonomous in daily life * Schellong test showing OH (drop of Systolic BP \>20 mmHg or Diastolic BP \>10 mmHg)(for study group with OH) or no OH (for studygroup without OH) * For women of childbearing potential: using or willing to use during the study a reliable contraception method compatible with MRI Exclusion…