Mechanistic insights into how Calcitonin gene-related peptide (CGRP) causes migraine and headache:  CGRP, a vasoactive peptide known to play a role in the pathophysiology of migraine, decreases the expression of PD-L1, aggravates acute and chronic pain, increases mechanical and thermal hypersensitivity and promotes nociceptive neuron excitability, via down-regulation of its target gene, 6/April/2019, 1.13 pm