Epidemiological studies have reported a reduction in the prevalence of Alzheimer's disease in individuals that ingest low amounts of alcohol. Also, it has been found that moderate consumption of ethanol might protect against beta-amyloid (A beta) toxicity. However, the mechanism underlying its potential neuroprotection is largely unknown. In the present study, we found that ethanol improved the cognitive processes of learning and memory in 3xTgAD mice. In addition, we found that a low concentration of ethanol (equivalent to moderate ethanol consumption) decreased the binding of A beta (1 and 5 mu M) to neuronal membranes and, consequently, its synaptotoxic effect in rat hippocampal and cortical neurons under acute (30 minutes) and chronic (24 hours) incubation conditions. This effect appears to be exerted by a direct action of ethanol on A beta because electron microscopy studies showed that ethanol altered the degree of A beta aggregation. The action of ethanol on A beta also prevented the peptide from perforating the neuronal membrane, as assayed with patch clamp experiments. Taken together, these results contribute to elucidating the mechanism by which low concentrations of ethanol protect against toxicity induced by A beta oligomers in primary neuronal cultures. These results may also provide an explanation for the decrease in the risk of Alzheimer's disease in people who consume moderate doses of alcohol. (C) 2015 Elsevier Inc. All rights reserved.