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Abstract Rilmenidine (2-[dicyclopropylmethyl]-amino-2-oxazoline) is a second- generation antihypertensive agent that decreases arterial pressure and sympathetic activity by an action in the central nervous system (CNS). It has a higher selectivity for imidazoline receptors compared with alpha2-adrenoceptors than does the first-generation imidazoline agent clonidine and is now being used clinically to treat hypertension without the side effects (including sedation) that are associated with alpha2-adrenoceptor agonists. The objective of this investigation was to study the cardiovascular effects of rilmenidine in rats. In vivo experiments studied the antihypertensive, antidysrhythmic, diuretic, natriuretic and kaluretic effect of rilmenidine as well as its effect on baroreceptors heart rate reflex. Ex vivo experiment studied the effect of rilmenidine on reactivity of rat’s isolated aortic rings. The results obtained demonstrated that: •Daily oral administration of L-NAME (40mg/kg/day) for four weeks in rats produced a significant increase in systolic blood pressure by 50.9%. While daily oral administration of rilmenidine, in a dose of 3 mg/kg/day, simultaneously with L-NAME prevented blood pressure increase during the four weeks period of the treatment.• Single oral dose of rilmenidine 3 mg/kg/day produced significant increase in Na+ & K+ concentrations in 24 hours rat’s urine by 91.96% and 73.65% respectively, and single oral dose of rilmenidine 10 mg/kg/day produced significant increase in Na+ & K+ concentrations in 24 hours rat’s urine by 150% and 101.6% respectively. While significant increase in 24 hours urine volume was only evident with rilmenidine dose of 10 mg/kg/day. •Oral pretreatment with rilmenidine (3mg/kg) four hours prior to injection of phenylephrine (5,10,20,40 µg/kg) increased the baroreceptor reflex sensitivity. •Rilmenidine (3 mg/ kg oral dose ) is prophylactic against epinephrine induced dysrhythmias i.e. premature ventricular contractions, in urethane anesthetized rats. |