LAUSR

AIMS Allergic rhinitis is a global cause of disability, characterized by airway inflammation. Sumatriptan is a 5-hydroxytryptamine 1B/1D (5HT1B/1D) agonist used as a treatment for migraine headaches. Activation of 5HT1B/1D receptors can inhibit the release of neuropeptides and inhibit the inflammation cascades. This study investigated the effect of sumatriptan on ovalbumin-induced allergic rhinitis model in mice and the role of nitric oxide. METHODS Female Balb/c mice were sensitized by intraperitoneal ovalbumin and challenged by intranasal ovalbumin. Mice received sumatriptan in doses 3, 10, 30 μg/kg intraperitoneally, 30 min before the last ovalbumin challenge. KEY FINDINGS Intraperitoneal injection of sumatriptan significantly decreased the nasal scratching, IL-4 and serum IgE levels of allergic mice, but it increased IFNγ levels. Histopathological analysis showed that the number of eosinophils was significantly elevated in nasal mucosa of ovalbumin-induced allergic mice, while sumatriptan treatment significantly reduced the number of eosinophils. GR-127935, a selective 5-HT1B/1D-receptor antagonist, reversed the anti-allergic effects of sumatriptan. Acute administration of l-NAME, a non-specific inhibitor of nitric oxide synthase, along with sumatriptan attenuated the anti-allergic effects of sumatriptan but chronic administration of l-NAME did not affect the influences of sumatriptan. Furthermore, sumatriptan decreased the inducible nitric oxide synthase (iNOS) protein expression in allergic mice, but it did not change the concentration of eNOS protein. SIGNIFICANCE This study shows that sumatriptan administration is associated with anti-allergic effects which are through 5HT1B/1D receptors. Decrease in iNOS expression and changes in T-helper 1&2 cytokines levels may indicate the involvement of inducible NOS and inflammation.