Role of endothelium on relaxant effect of geraniol in isolated rat aorta

This study aimed to investigate the vascular effect of geraniol, a monoterpene essential oils that is found in some medicinal plants, in rat thoracic aorta. The thoracic aorta was isolated, cut into rings, mounted in organ-bath chambers containing Krebs’s solution (37°C, 95%O2 and 5%CO2) and equilibrated in resting tension (2g) for 60 min. Isometric tension was recorded under the treatments with vasoconstrictors, geraniol, and various drugs as pharmacological interventions. The effect of geraniol on the contractions evoked by noradrenaline (10μM) was tested after 20 min pre-incubation of aortic rings with increasing concentrations of geraniol in the bath. In various experiments the endothelium- intact or -denuded aortic rings contracted by 80 mM potassium chloride. When contraction was stable geraniol was applied. Relaxation was expressed as % reduction or reversal of initial contraction induced by vasocative agents. The possible participation of nitric oxide (NO), intracellular cyclic GMP and prostacyclin in the relaxant effects of geraniol, were studied by incubating (for 20 min) some rings with the NO synthase inhibitor N-nitro-L-arginine methyl ester (L-NAME, 200 μM), methylene blue(10 μM) and indomethacin (10μM), respectively. Geraniol in dose dependent manner reduced the contractile response to noradrenalin and relaxed of KCl induced active tone in rat aorta. Relaxant effects of geraniol on the KCl induced contraction was not modified by L-NAME, methylene blue and indomethacin. In conclusion geraniol induced dose dependent relaxation in rat aorta, which was endothelium-independent.