Nitric oxide (NO) is a signaling molecule that is synthesized from L-arginine by NO synthase [21]. It is well recognized that NO plays an important role in maintaining the normal physiological function of vascular tissues. It has been previously reported that histamine increased vascular permeability by activating NO production [22]. In addition,
Mayhan [23] also demonstrated that nitric oxide was involved in increased macromolecular extravasation induced by histamine in the hamster cheek pouch. In addition, endothelial nitric oxide synthase (eNOS) was found to play a major role in vascular leakage during acute inflammation in vivo [24]. Thus, suppression of NO production may help reduce acute inflammation. From the present study, it was observed that more than 50% of the NO elevation caused by histamine could be alleviated by AEBO. This further supports its action as an antiinflammatory agent.