Roles of thromboxane A2 and 5-hydroxytryptamine in endotoxin-induced digital vasoconstriction in horses

Abstract

Objective - To evaluate the roles of 5-hydroxytryptamine (5-HT), thromboxane A2 (TxA2), and platelet-activating factor (PAF) in endotoxin-induced digital hypoperfusion in horses. Animals - 6 healthy adult Thoroughbreds. Procedures - Horses were treated with IV administration of saline (0.9% NaCl) solution (control treatment) or the 5-HT1B/D selective antagonist, GR55562 (0.3 mg/kg), prior to tryptamine infusion (1.6 μg/ kg/min or 30 minutes) to establish an effective GR55562 dose. In a crossover study, horses were treated with IV administration of saline solution (control treatment), aspirin (4 mg/kg, 2 hours or 4 days before lipopolysaccharide [LPS] infusion), GR55562 (0.3 mg/kg), the PAF a..