Platelet-activating factor (Paf) antagonist, WEB 2086, protects against Paf-induced hypotension in Macaca...

1. The actions of intravenously administered platelet-activating factor (Paf) (0.1-3.33 nmol kg-1) and the effect of a recently described Paf antagonist, WEB 2086, were investigated in the anaesthetized open-chest monkey, Macaca fascicularis. 2. Paf dose-dependently reduced blood pressure, left ventricular pressure (LVP) and its first differential LV dP/dt. 3. Mean pulmonary artery pressure, recorded in three animals, was essentially unchanged by any dose of Paf. 4. WEB 2086 (0.22 mumol kg-1, i.v.) attenuated the Paf-induced changes in BP, LVP and LV dP/dt. The dose-response curve for fall in BP was shifted to the right by one order of magnitude. 5. Histamine-induced cardiovascular changes (systemic hypotension and tachycardia) were not affected by prior administration of WEB 2086. 6. WEB 2086 should be of value in assessing the role of Paf in pathophysiological conditions.