OPN4 and migraine disorder: We performed double immunostaining for calcitonin gene-related peptide (CGRP), a neuropeptide implicated in migraine (Eftekhari et al., 2015; Russo, 2015), and PACAP, which colocalizes with melanopsin in ipRGCs (Hannibal et al., 2004), to determine the identity of melanopsin-expressing TG neurons.