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.