This study investigated the cardiovascular effects of the
essential oil of Croton zehntneri (EOCZ) in
deoxycorticosterone-
acetate (
DOCA)-
salt hypertensive rats. Furthermore, in vitro experiments using isolated thoracic aortic rings were performed to assess the vascular effects of the EOCZ. In conscious hypertensive rats, intravenous (i.v.)
injections of EOCZ (1-20 mg/kg) induced rapid (2-4 s) and dose-dependent
hypotension and
bradycardia (phase 1). The
hypotension was followed by a significant pressor effect that was more evident at the higher doses (10 and 20 mg/kg) of EOCZ.
Hypotension and
bradycardia of EOCZ (phase 1) were abolished and respectively reversed into pressor and tachycardiac effects by
methylatropine (1 mg/kg, i.v.) pretreatment. In isolated endothelium-intact aortic preparations, increasing concentrations (1-1000 microg/mL) of EOCZ relaxed the
potassium-induced contraction in a concentration-dependent manner with an IC50 (geometric mean [95% confidence interval]) value of 202.0 [92.0-443.7] microg/mL. This
vasorelaxant effect remained unaffected by either mechanical removal of functional vascular endothelium (IC50 = 189.0 [159.4-224.7] microg/mL) or the addition of
atropine (1 microM) (IC50 = 158.6 [79.8-316.2] microg/mL) in the perfusion medium. These data show that i.v. administration of EOCZ in
DOCA-
salt hypertensive rats induces a vago-vagal reflex decreases in heart rate and blood pressure (phase 1). EOCZ may induce a second and delayed
hypotension due to its direct endothelium-independent
vasorelaxant effects, but it seems to be buffered by the pressor component (subsequent to phase 1) of EOCZ. This pattern of blood pressure and heart rate responses to EOCZ seems unaltered by
DOCA-
salt hypertension, as was similar to that previously reported in conscious normotensive rats.