Fig. 1

The human provocation model involves IV infusion of a provoking substance (see insert) usually for 20 min. Headache, blood pressure, heart rate and the diameter of superficial temporal- and radial arteries and velocity of blood in the middle cerebral artery are monitored at short intervals. After discharge a headache diary is kept every hour until 12 h after the provocation. Many substances cause migraine in this model.Modified from previous publications