VIP and migraine disorder: A number of well-studied mechanisms that are probably involved in migraine pathogenesis are as follows: trigeminovascular pain pathway, proinflammatory cytokines, and neuroinflammation, and also the activity of some factors such as nitric oxide and neuropeptides including calcitonin gene-related peptide (CGRP), substance P, neurokinin A, neuropeptide Y (NPY), vasoactive intestinal peptide (VIP), and pituitary adenylate cyclase-activating polypeptide (PACAP) (5–9).