Cardiovascular effects of Hyptis fruticosa essential oil in rats

In non-anesthetized normotensive rats, Hyptis fruticosa essential oil (HFEO, 5, 10, 20 and 40 mg/kg; i.v.) induced hypotension associated with tachycardia. In intact and isolated rings of rat superior mesenteric artery (control), HFEO (1–1000 μg/ml, n = 6, cumulatively) induced concentration-dependent relaxations of tonus induced by 10 μM phenylephrine (Phe) (pD2 = 2.6 ± 0.27; Emax = 64 ± 8.3%). In denuded endothelium pre-contracted rings with Phe or K+-depolarizing solution (80 mM), the concentration–response curves to HFEO were not shifted (pD2 = 2.3 ± 0.25 and 2.3 ± 0.28, respectively), but their maximal responses were significantly (P < 0.05 vs control) increased (Emax = 122.3 ± 18.2% and 92 ± 3.6%, respectively). HFEO was also capable of antagonizing the concentration–response curves to CaCl2 (3 μM–30 mM) in a dose-dependent manner.