CALCA and migraine disorder: Finally, although CGRP is strongly implicated in the generation of migraine, largely but not exclusively via its peripheral vasodilatory action (Brain et al., 1985), systemic injection of nitroglycerin, which triggers migraine in humans and profound mechanical hypersensitivity in animals (Bates et al., 2010), did not induce Fos in the CGRP interneurons (Figure 8—figure supplement 1b).