A Potential Preclinical Migraine Model: CGRP-Sensitized Mice.

The neuropeptide calcitonin gene-related peptide (CGRP) plays a key role in migraine. However, a major challenge for studying CGRP actions is the lack of animal models for migraine. Clinical studies suggested that migraineurs are more sensitive to CGRP than people who do not suffer from migraine. We therefore generated a transgenic mouse that is sensitized to CGRP (nestin/hRAMP1 mice). The mice have elevated expression of a subunit of the CGRP receptor, human receptor activity-modifying protein 1 (hRAMP1). Nestin/hRAMP1 mice have two symptoms of migraine: photophobia and mechanical allodynia. The light aversion was greatly enhanced by intracerebroventricular administration of CGRP. CGRP had little effect on motility in the light zone, but once in the dark, the mice moved less than controls. The CGRP-induced light aversion was attenuated by co-administration of the CGRP receptor antagonist olcegepant. These findings suggest that CGRP acts as a neuromodulator to increase sensory responses and that regulation of a single gene, hRAMP1, could potentially contribute to migraine susceptibility.