Mechanisms leading to increased TRPV1 expression in chronic migraine patients are unclear, but preclinical studies using repeated 30-day administration of eletriptan or indomethacin found increased TRPV1 (and TRPA1) in the trigeminal ganglia, so migraine itself may upregulate the channel and/or migraine therapeutics may also have this potential [62]. This evidence concerns the gene TRPA1 and migraine disorder.