Enhanced hypotensive effects of the essential oil of Ocimum gratissimum leaves and its main constituent, eugenol, in DOCA-salt hypertensive conscious rats

Abstract The cardiovascular effects of intravenous (I. V.) treatment with the essential oil of OCIMUM GRATISSIMUM (EOOG) and its main constituent, eugenol (Eug) were investigated in the experimental model of deoxycorticosterone acetate (DOCA-salt)-hypertensive rats. In both conscious DOCA-salt hypertensive rats and their uninephrectomized controls, I. V. bolus injections of EOOG (1 - 20 mg/kg) or Eug (1 - 10 mg/kg) induced dose-dependent hypotension and bradycardia. Treatment with DOCA-salt significantly enhanced the maximal decreases in mean aortic pressure (MAP) elicited by hexamethonium (30 mg/kg, I. V.) as well as the hypotensive responses to both EOOG and Eug without affecting the bradycardia. However, the enhancement of EOOG-induced hypotension in hypertensive rats remained unaffected by I. V. pretreatment with either hexamethonium (30 mg/kg) or methylatropine (1 mg/kg). These results show that I. V. treatment with EOOG or Eug dose-dependently decreased blood pressure in conscious DOCA-salt hypertensive rats, and this action is enhanced when compared with uninephrectomized controls. This enhancement appears related mainly to an increase in EOOG-induced vascular smooth relaxation rather than to enhanced sympathetic nervous system activity in this hypertensive model.