It could be hypothesized that the ability to enter the central nervous system (CNS), as well as the high concentration of PACAP38 and its receptors in the hypothalamus, known to be involved in the prodromal phase of the migraine cycle, could explain the higher incidence of premonitory symptoms administering PACAP38 compared to CGRP [24]. The gene discussed is CALCA; the disease is migraine disorder.