Neurochemistry of scalp arteries innervation from patients suffering with chronic migraine

Several data suggest that scalp arteries and the vanilloid receptor TRPV1, calcitonin gene related peptide (CGRP) and substance P (SP) are involved in chronic migraine (CM). We examined the aspect and density of TRPV1-, CGRP-, and SP-immunoreactive innervation in surgical specimens of human scalp arteries from treatment-resistant CM patients and control subjects. Patients gave informed consent. The length of immunoreactive nerve fibres in vessel cross sections was quantified by computerised image analysis. Density of innervation was evaluated as ratio of the total fibre length to the vessel section area and evaluated in relation to the total innervations revealed by the pan-neuronal structural nerve marker protein gene product 9.5 (PGP9.5). Average of innervation in CM and control specimens showed statistically significant differences for TRPV1 (p=.009), CGRP (p=.001) and SP (p=.037), and not for PGP9.5 (p=.31) (t-test). Analysis of ratio of TRPV1-, CGRP- and SP-positive fibers to PGP9.5-positive ones for each artery gave a statistically significant higher amount of TRPV1-positive fibres in CM compared to control samples (p<.02, U-test). Peptide-positive fibers, though more abundant in CM tissue, did not significantly differ between the two groups. Compared to controls, in subjects affected by CM, the innervation immunoreactive to TRPV1 and, to a lower degree, to the peptides CGRP and SP is increased. This supports the viewpoint of a role of scalp arteries and the involvement of TRPV1 and possibly CGRP and SP in CM. Funded by FBS