ABSTRACT. Characteristics of the signal transduction in Platelet activating factor (PAF)-activated platelets and effects of anti-platelet agents on this response were investigated in vitro for potential therapeutic applications in canine endotoxemia. Blockade of the PAF receptor by a specific blocker has the strongest inhibitive effect on the PAF-induced platelet reactions. The response was also inhibited by either Ca 2+ channel blockers or prostaglandin E 1 .KEY WORDS: canine platelet, inhibitor, platelet activating factor.