Since some migraine patients do not respond to treatments that either target CGRP or its receptor, other substrates have been explored for their potential implication in migraine pathogenesis: among them, other neuropeptides (i.e., pituitary adenylate cyclase-activating polypeptide, VIP, amylin, and adrenomedullin), nitric oxide, and phosphodiesterase-3 and -5 appeared able to induce migraine-like attacks through vasodilation of intracranial arteries in human provocation studies (31). Here, VIP is linked to migraine disorder.