Aim: To investigate whether or not peroxynitrite scavenging improves dexmedetomidine-induced contractions of rat aortae after 24 and 96 h treatment with lipopolysaccharide (LPS).Methods: Eight to ten weeks old male SD rats were injected intraperitoneally with (1 mg/kg) of LPS or normal saline.Twenty-four and ninety-six hours later, their aortae were harvested.