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 sensitiz ed rats. The i.v. injection of the antigen (ovalbumin, 250 or 500 mu g /kg), induced a systemic anaphylactic reaction mainly characterized by sudden and marked arterial hypotension and high mortality rates. Yang ambin, a PAF receptor antagonist isolated from the Brazilian plant Oco tea duckei Vattimo (Lauraceae), as well as the reference PAF receptor antagonist SR 27417, significantly prevented and partially reversed th e circulatory collapse elicited by antigen challenge. Moreover, yangam bin and SR 27417, when administered 5 min before re-exposure of the an imals to the antigen, markedly improved the survival rate at 120 min. These results confirm that PAF plays an important role in the pathophy siology of anaphylactic shock and show that yangambin presents good th erapeutic potential in the treatment of the cardiovascular alterations observed during immediate hypersensitivity reactions.