Effects of cloxyquin on the pain and neurogenic inflammation in migraine in the in-vivo and ex-vivo experimental models in rats

We investigated effects of TRESK activation on pain behavior and mechanisms responsible for migraine using in-vivo and ex-vivo models. In-vivo migraine model was induced by nitroglycerin (NTG). Vehicle of NTG or other drugs, three different doses of TRESK activator cloxyquin (1, 10 and 50 mg/kg), TRESK inhibitor A2764(10 mg/kg) and sumatriptan (1 mg/kg) were administered alone or in combination 75 min after NTG. In ex-vivo hemiskull, trigeminal ganglion and brainstem preparations, CGRP release was induced by capsaicin, and direct effect of drugs tested on CGRP release was investigated. Mechanical hyperalgesia was measured by von-Frey test, serum, trigeminal ganglion and brainstem CGRP, and brainstem c-Fos concentrations by ELISA. Number and degranulation of meningeal mast cells were determined by toluidine-blue staining. In-vivo data were analyzed by one-way ANOVA, and ex-vivo data were analyzed by repeated measures ANOVA. In in-vivo model, cloxyquin dose-dependently reduced NTG-induced mechanical hyperalgesia, c-fos expression, CGRP release, and meningeal mast cell activation and number (p<0.05). TRESK inhibitor A2764 reversed effects of cloxyquin, confirming that these effects were mediated by TRESK activation(p<0.05). In ex-vivo preparations, cloxyquin reduced capsaicin-induced CGRP release(p<0.05) but didn't affect basal CGRP release. A2764 reversed the effects of cloxyquin(p<0.01) and facilitated CGRP release. While sumatriptan alleviated NTG- and capsaicin-induced effects(p<0.05), cloxyquin enhanced effect of sumatriptan(p<0.05). Cloxyquin dose-dependently alleviates pain behavior and increased levels of CGRP and c-Fos, and mast cell count and activation, which are components of neurogenic inflammation, in migraine model. These results suggest that TRESK channels may be a promising new target in migraine treatment.