Effects of Phikud Navakot extract on vascular reactivity in the isolated rat aorta

The aim of the present study is to investigate the effect of standardized Phikud Navakot extract (NVKE) on aortic rings from male Sprague Dawley rats. Changes in tension were measured using an isometric force transducer and recorded on the PowerLab recording system. Vasorelaxant effect of NVKE was examined in the presence of indomethacin (10 microM), N(G)-nitro L-arginine methyl ester (L-NAME, 300 microM), methoxamine (0.1-300 microM), carbachol (1 nanoM-30 microM), or sodium nitroprusside (0.1 nanoM-10 microM). The results showed that NVKE (1-300 microg/mL) caused vasorelaxation in a concentration-dependent manner with a pEC50 value of 4.27 +/- 0.24 and R(max) of 67.7 +/- 13.9%. Pretreatment with indomethacin or L-NAME did not affect NVKE-induced vasorelaxation. However, co-incubation of indomethacin and L-NAME significantly reduced (p < 0.05) vasorelaxation to NVKE (100 microg/mL). Pre-treatment with NVKE significantly decreased (p < 0.05) endothelium-dependent relaxations to carbachol (R(max) = 52.90 +/- 14.3%), but not to sodium nitroprusside. Moreover contractions to methoxamine were unaffected after pretreatment with NVKE. The present study suggested that NVKE decreased vasorelaxation to carbachol in the rat aorta, which may exert at least against muscarinic receptors. These findings support the use of Phikud Navakot, a major ingredient of Yahom Navakot, against dizziness and fainting.