Trolox is a hydrophilic analogue of vitamin E and a free radical scavenger. Ethanol diminishes the amplitude of spontaneous contractions and acetylcholine (ACh)-induced contractions in rabbit duodenum. The aim of this work was to study the effect of trolox on the alterations induced by ethanol on contractility and lipid peroxidation in the duodenum. The duodenal contractility studies in vitro were carried out in an organ bath and the levels of malondialdehyde and 4-hydroxyalkenals (MDA+4-HAD) were measured by spectrophotometry. Trolox increased the reduction induced by ethanol on the amplitude of spontaneous contractions in longitudinal muscle but not in circular muscle. Trolox 4 mM decreased the effects of ethanol on ACh-induced contractions and on MDA+4-HDA concentrations. We conclude that trolox might prevent oxidative stress induced by ethanol in the duodenum. INTRODUCTIONAlcohol is a hydroxyl compound that can be present in the diet. The amount and type of alcohol consumed and the frequency of its consumption can vary tremendously and can have divergent effects on an organism (1,2). The deleterious effects of alcohol, at least partly, involve alcohol induced oxidative injury that has been documented by measurement of oxidant radicals (3-5). The organism has developed a complex defense system which is composed of free radical scavenger molecules such as vitamins and antioxidative enzymes.Ethanol induces inhibition of esophageal, gastric and intestinal contractility (6-9). The inhibition produced by ethanol is attributed to an inhibition of Ca 2+ influx in the canine jejunal circular muscle and in human and cat esophageal contractility (7,8). Alcohol also inhibits the motility of the sphincter of Oddi in vitro (10,11) and the colon (12). In a previous study, we demonstrated the inhibitory effects of ethanol on the spontaneous contractions and ACh-induced contractions in rabbit duodenum, which are reduced by Ca 2+ -activated K + channel antagonists (13). Ethanol also provokes an inhibition of gastric emptying and small intestinal transit that is mediated by type A CCK receptors or capsaicin-sensitive neural pathways (14-16). However, ethanol produces contractile actions in guinea pig gastric smooth muscle, which required extracellular calcium and are blocked by tyrosine kinase inhibitors (17).Trolox, a phenolic antioxidant, originally designed for food preservation, has a chromane structure similar to atocopherol or vitamin E (18,19). Trolox decreases hepatocellular damage during sepsis (20) and abrogates oxidative stress during cold small bowel storage (21).Although antioxidants can attenuate alcohol-induced injury, there is no single antioxidant that protects all organs during all modes of exposure (3). There is very little documentation available on the effect of trolox on intestinal motility. In addition, alcohol induces oxidative stress and REV ESP ENFERM DIG (Madrid) Vol. 103. N.° 8, pp. 396-401, 2011 Received: 10-01-11. Accepted: 18-03-11.