IMPORTANCE Vasoactive intestinal polypeptide (VIP) and pituitary adenylate cyclase-activating polypeptides (PACAPs) are structurally and functionally related, yet different in their migraineinducing properties. It remains unclear whether the lack of migraine induction can be attributed to the only transient vasodilatory response after a 20-minute infusion of VIP. OBJECTIVE To determine whether a 2-hour infusion of VIP would provoke migraine attacks. DESIGN, SETTING, AND PARTICIPANTS A randomized, double-blind, placebo-controlled, crossover study was conducted between May and September 2020 at the Danish Headache Center in Copenhagen, Denmark. Patients were eligible for inclusion if they were ages 18 to 40 years, weighed between 50 and 90 kg, had a diagnosis of migraine without aura as defined by the International Classification of Headache Disorders, and had a migraine frequency of 1 to 6 attacks per month. INTERVENTIONS Patients were randomly allocated to receive a 2-hour infusion of VIP or placebo on 2 different days. MAIN OUTCOMES AND MEASURESThe primary end point was the difference in incidence of experimentally induced migraine attacks during the observational period (0-12 hours) between VIP and placebo. RESULTS Twenty-one patients (17 [81%] women and 4 [19%] men; mean [range] age, 25.9 [19-40] years) were recruited in the study. Fifteen patients (71%; 95% CI, 48%-89%) developed migraine attacks after VIP compared with 1 patient (5%; 95% CI, 0%-24%) who developed a migraine attack after placebo (P < .001). The VIP-induced migraine attacks mimicked patients' spontaneous attacks.The area under the curve (AUC) of headache intensity scores (0-12 hours), as well as the AUC of the superficial temporal artery diameter (0-180 minute) were significantly greater after VIP compared with placebo (AUC 0-12h , P = .003; AUC 0-180min , P < .001).

Objective To determine whether glibenclamide, a non-selective adenosine 5′-triphosphate-sensitive K+ (KATP) channel blocker, attenuates pituitary adenylate cyclase-activating polypeptide-38 (PACAP38)-induced headache and vascular changes in healthy volunteers. Methods In a double-blind, randomized, placebo controlled and crossover design, 22 healthy volunteers were assigned to receive an intravenous infusion of 10 picomole/kg/min pituitary adenylate cyclase-activating polypeptide-38 over 20 minutes followed by oral administration of 10 mg glibenclamide or placebo. The primary endpoint was the difference in incidence of headache (0–12 hours) between glibenclamide and placebo. The secondary endpoints were a difference in area under the curve for headache intensity scores, middle cerebral artery velocity (VmeanMCA), superficial temporal artery diameter, radial artery diameter, heart rate, mean arterial blood pressure and facial skin blood flow between the two study days. Results Twenty participants completed the study. We found no difference in the incidence of pituitary adenylate cyclase-activating polypeptide-38-induced headache after glibenclamide (19/20, 95%) compared to placebo (18/20, 90%) ( P = 0.698). The area under the curve for headache intensity, middle cerebral artery velocity, superficial temporal artery diameter, radial artery diameter, facial skin blood flow, heart rate and mean arterial blood pressure did not differ between pituitary adenylate cyclase-activating polypeptide-38-glibenclamide day compared to pituitary adenylate cyclase-activating polypeptide-38-placebo day ( P > 0.05). Conclusions Posttreatment with 5′-triphosphate-sensitive K+ channel inhibitor glibenclamide did not attenuate pituitary adenylate cyclase-activating polypeptide-38-induced headache and hemodynamic changes in healthy volunteers. We suggest that pituitary adenylate cyclase-activating polypeptide-38-triggered signaling pathway could be mediated by specific isoforms of sulfonylurea receptor subunits of 5′-triphosphate-sensitive K+ channels and other types of potassium channels.