Effect of Riocigaut on Cerebral Vasodilation and Headache Induction in Healthy Volunteers

Inclusion Criteria: * Ability to provide written informed consent and receive participant privacy and rights information. * Male or female participants aged 18-45 years. * Weight between 50-100kg * Non-smokers Exclusion Criteria: * Any current or previous known primary or secondary headache disorder(s) apart from tension type headache ≤ 1 day per month. * Headache \<48 hours before study start. * Daily use of any medication except contraceptives. Specifically use of nitrates or nitric oxide donors or phosphodiesterase inhibitors. * Intake of any pro necessitate medication later than 4 times plasma half-life for the specific drug before study start, except for contraceptives * Women of child-bearing potential not currently using safe contraceptives. Women of child-bearing potential does not include hysterectomized women and women who have been in menopause for at least 2 years. Safe contraceptives include either IUD, birth control pills, surgical sterilization of the woman, depositary gestagen, barrier prevention or sexual abstinence. * Pregnant or breastfeeding women * Positive pregnancy urin screening on screening day or study days. * A medical history or clinical signs of * Hypertension (systolic blood pressure \>140mmHg and/or diastolic blood pressure \>90mmHg) * Hypotension (systolic blood pressure \<100mmHg and/or diastolic blood pressure \<50mmHg) * Electrocardiogram (ECG) with any clinically significant abnormalities at screening determined by the investigator, including but not limited to, prolonged PQ or QTc interval, signs of arrythmias, ischemia or left/right ventricle dysfunction/hypertrophy. * Blood work at screening with signs of anemia. * Blood work at screening with signs of abnormal kidney and liver function. * A medical history or clinical signs of cardiovascular disease including cerebrovascular disease. * A medical history or clinical signs of pulmonary disease. * A medical history or clinical signs of liver, renal, gastrointestinal, endocrine, hematological or neurological disease. * A medical history or clinical signs of psychiatric illness or substance abuse * A medical history or clinical signs of drug or alcohol abuse * A medical history or clinical signs of disease of any origin that the investigative doctor finds relevant for participation in the study * A family history of severe cardiac disease. * Any history of hypersensitivity to riociguat. * Subjects who do not want information about crucial pathological findings during the study