Vasorelaxant effects of 1-nitro-2-phenylethene in isolated rings of rat aorta

Nitro-2-phenylethane (NPEa) is a vasorelaxant constituent of the essential oil of Aniba canelilla. Here, we investigated whether 1-nitro-2-phenylethene (NPEe), a derivative molecule obtained synthetically, has similar properties in isolated rings of rat aorta. Trace recordings were obtained isometrically. NPEe (0.1–100µg/ml) had no effect on aortic rings under resting tonus, but relaxed sustained contractions induced by phenylephrine (PHE, 1µM) in endothelium-intact preparations (IC₅₀=6.01±1.62µg/ml; n=6). This vasorelaxation remained unaltered by vascular endothelium removal (IC₅₀=4.56±0.75µg/ml; n=5), but was significantly reduced by pretreatment with 10µM ODQ (IC₅₀=26.18±7.54µg/ml, n=9). NPEe also relaxed the contractions evoked by 60 mM K⁺ with the same potency for relaxing PHE without influence of endothelium removal. In Ca²⁺-free medium, NPEe (1–3µg/ml) inhibited contractions induced by exogenous Ca²⁺ (0.1–20 mM) addition in preparations depolarized by K⁺, but was inert against PHE-induced phasic contractions in presence of verapamil (1µM; n=9). NPEe inhibited contractions caused by extracellular Ca²⁺ restoration in thapsigargin-treated aorta in Ca²⁺-free medium. Thus, as NPEa, NPEe has vasodilator properties in rat aortic rings, which seem potentially mediated through a guanylate cyclase pathway.