The Effects of a Long-lasting Infusion of Vasoactive Intestinal Peptide (VIP) on Headache, Cranial Hemodynamic and Autonomic Symptoms in Healthy Volunteers

12 healthy volunteers of both genders will be included in the main study. Participants will meet twice, with at least one week in between. The main study is a double-blind, randomized, cross-over trial among placebo (sterile saline, non-active substance) and VIP. Intravenous infusion of VIP / placebo (saline) will be conducted over 120 minutes. Patients will be asked after each trial day to record headache strength, accompanying symptoms, and drug use for up to 24 post-infusion.