PTH and migraine disorder: The intravenous infusion of PACAP-38 might also induce cephalic pain in people with PTH through mast cell degranulation, activating meningeal nociceptors.28,29 Mast cells, abundant in the meninges, play a key role in inflammatory responses.29,30 PACAP-38 is thought to trigger mast cell degranulation in humans, likely via its MRGX2 receptor.31 This degranulation releases histamine, a pro-nociceptive agent that induces migraine attacks and dilates meningeal arteries.32,33 The precise role of histamine in PACAP-38-induced dilation of meningeal arteries is uncertain.