Headaches are extremely common illnesses with a combined lifetime prevalence of 90-99% in Europe. Despite this high prevalence, there are persons who have never, in their whole life, encountered a headache.

The aim of the study is to identify factors that protect against headache by studying multiomics in people who never have had a headache (headache resistant) versus non-resistant controls.

The investigators will measure multiomic changes (transcriptomics and metabolomics) after headache provocation with isosorbide mononitrate. 3 blood samples, two for RNA and one for metabolomics are taken right before administration of isosorbide mononitrate, 3 hours after administration of isosorbide mononitrate and again 5 hours after administration of isosorbide mononitrate.

The investigators hope to contribute with novelty to the current understanding of headache pathophysiology and development of more efficient treatment of headache.

Inclusion Criteria:

• Headache resistant and non-resistant male participants from the Danish Blood Donor Study.
• Weight: 45 kg to 95 kg

Exclusion Criteria:

• Daily consumption of any medication.
• Consumption of any medication less than 12 hours prior to the study day.
• Headache on the study day or 48 hours prior to the study day.
• Amnestic or clinical signs of hypertension (systolic blood pressure >150 mmHg and/or diastolic blood pressure >100 mmHg) or hypotension (systolic blood pressure <90 mmHg and/or diastolic blood pressure <50 mmHg).
• Any severe cardiovascular disease, including cerebrovascular illness.
• Amnestic or clinical signs of current mental illness.
• Amnestic or clinical signs of current substance or drug abuse.
• Amnestic or clinical signs of any illness the responsible doctor considers relevant for participation in the study.