• K Ibrahimi, S Vermeersch, Ahj Danser, C M Villalón, A H van den Meiracker, J de Hoon, and A MaassenVanDenBrink.
• Division of Vascular Medicine and Pharmacology, Department of Internal Medicine, Erasmus University Medical Center, the Netherlands.
• Cephalalgia. 2014 Jun 1; 34 (7): 514-22.

BackgroundDuring migraine, trigeminal sensory nerve terminals release calcitonin gene-related peptide (CGRP), inducing nociception and vasodilation. Applied on the skin, capsaicin activates the transient receptor potential vanilloid type 1 (TRPV1) channel and releases CGRP from sensory nerve terminals, thus increasing dermal blood flow (DBF). Using capsaicin application and electrical stimulation of the forehead skin, a trigeminal nerve-innervated dermatome, we aimed to develop a model to measure trigeminal nerve-mediated vasodilation in humans.MethodsUsing laser Doppler imaging, forehead DBF responses to application of capsaicin (0.06 mg/ml and 6.0 mg/ml) and saline, with and without iontophoresis, were studied in healthy subjects. The within-subject coefficient of variation (WCV) of repeated DBF measurements was calculated to assess reproducibility.ResultsMaximal DBF responses to 6.0 mg/ml capsaicin with and without iontophoresis did not differ (Emax 459 ± 32 and 424 ± 32 arbitrary units (a.u.), WCV 6 ± 4%). In contrast, DBF responses to 0.06 mg/ml capsaicin were significantly larger with than without iontophoresis (Emax 307 ± 60 versus 187 ± 21 a.u., WCV 21 ± 13%). Saline with iontophoresis significantly increased DBF (Emax: 245 ± 26 a.u, WCV 11 ± 8%), while saline application without iontophoresis did not affect DBF.ConclusionTopical application of capsaicin and electrical stimulation induce reproducible forehead DBF increases and therefore are suitable to study trigeminal nerve-mediated vasodilation in humans.© International Headache Society 2014 Reprints and permissions: sagepub.co.uk/journalsPermissions.nav.

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