Protective effects of Yangambin - a naturally occurring platelet-activating factor (PAF) receptor antagonist - on anaphylactic shock in rats.

The purpose of this study was to investigate the ability of yangambin to inhibit cardiovascular collapse and to reduce the mortality due to systemic anaphylaxis induced by antigen challenge in actively sensitized rats. The i.v. injection of the antigen (ovalbumin, 250 or 500 μg/kg), induced a systemic anaphylactic reaction mainly characterized by sudden and marked arterial hypotension and high mortality rates. Yangambin, a PAF receptor antagonist isolated from the Brazilian plant Ocotea duckei Vattimo (Lauraceae), as well as the reference PAF receptor antagonist SR 27417, significantly prevented and partially reversed the circulatory collapse elicited by antigen challenge. Moreover, yangambin and SR 27417, when administered 5 min before re-exposure of the animals to the antigen, markedly improved the survival rate at 120 min. These results confirm that PAF plays an important role in the pathophysiology of anaphylactic shock and show that yangambin presents good therapeutic potential in the treatment of the cardiovascular alterations observed during immediate hypersensitivity reactions.