Melatonin pretreatment improves gastric mucosal blood flow and maintains intestinal barrier function during hemorrhagic shock in dogs

OBJECTIVE Melatonin improves hepatic perfusion after hemorrhagic shock and may reduce stress-induced gastric lesions. This study was designed to investigate whether pretreatment with melatonin may influence gastric mucosal microcirculatory perfusion (μflow), oxygenation (μHbO2 ), or intestinal barrier function during physiological and hemorrhagic conditions in dogs. METHODS In a randomized crossover study, five anesthetized foxhounds received melatonin 100 μg kg-1 or vehicle (ethanol 5%) intravenously in the absence or presence of hemorrhagic shock (60 minutes, -20% blood volume). Systemic hemodynamic variables, gastric mucosal perfusion, and oxygenation were recorded continuously; intestinal barrier function was assessed intermittently via xylose absorption. RESULTS During hemorrhagic shock, melatonin significantly attenuated the decrease in μflow, compared with vehicle (-19±9 vs -43±10 aU, P