Ruthenium red selectively attenuates capsaicin induced vasodilation in pig nasal mucosa

The effect of ruthenium red, a blocker of transmembrane Ca2+ fluxes, on vasodilation in pig nasal mucosa induced by capsaicin, nicotine, bradykinin or histamine was evaluated in an in vivo preparation. To decrease toxic systemic effects pretreatment with ruthenium red was performed locally, intra-arterially in a nasal artery. Pretreatment with two doses of ruthenium red was evaluated (0.25 and 2.5 mg kg-1). Ruthenium red, in the low dose, resulted in a marked attenuation of the capsaicin-induced nasal vasodilation while the effect on the nicotine-induced vasodilation was not as prominent. Pretreatment with the high dose significantly blocked the vasodilatory effects of capsaicin, nicotine, bradykinin and histamine. Our series indicates that low concentration ruthenium red selectively modulates capsaicin induced vasodilation in pig nasal mucosa in vivo, probably via a direct blocking effect on cation channels opened by capsaicin. A high concentration of ruthenium red may exert a general inhibitory effect on transmembrane Ca2+ transport.