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Background: The bradykinin potentiating peptides (BPPs) are oligopeptides found in different animal venoms. BPPs isolated from Bothrops jararaca venom were the first natural inhibitors described for somatic angiotensin I-converting enzyme (ACE). They were used in the structural modeling for captopril development, a classical ACE inhibitor widely used to treat human hypertension. Methods: We evaluated the effect of BPP-5a on cardiovascular parameters of conscious Wistar (WTs) and spontaneously hypertensive rats (SHRs). Results: In SHR, BPP-5a showed potent cardiovascular effects, at doses ranging from 0.47 to 710 nmol/kg. The maximal changes in mean arterial pressure (MAP) and heart rate (HR) were found at the dose of 2.37 nmol/kg (Δ MAP: −38 ± 4 mmHg, p < 0.01; Δ HR: −71 ± 17 bpm, p < 0.05). Reductions in MAP and HR occurred throughout 6 hours of post-injection period. In contrast to active site-directed ACE inhibitors, no ACE inhibition, evaluated by the Ang I pressor effect, or bradykinin potentiation was observed during the antihypertensive effect of the pentapeptide. In vitro assays showed no effects of BPP-5a upon argininosuccinate synthetase and B1, B2, AT1, AT2 or Mas receptors. Ex vivo assays showed that BPP-5a induced endothelium-dependent vasorelaxation in isolated aortic rings of SHRs and WTs. Conclusions: Although the BPP-5a is considered an ACE inhibitor, our results indicate that its antihypertensive effect is exerted via a unique target, a nitric-oxide-dependent mechanism.