CALCA and migraine disorder: In the EWcp, several migraine-related neurotransmitters, neuromodulators, and receptors were found (eg, pituitary adenylate cyclase-activating polypeptide, pituitary adenylate cyclase-activating polypeptide type I receptor,31,66,78 neuronal nitric oxide synthase,91 substance P65), including calcitonin gene–related peptide (CGRP) fibers.90