Glyoxalase 1 (Glo1) is the first enzyme involved in glutathione-dependent detoxification of methylglyoxal, eventually generating D-lactate by the second enzyme glyoxalase 2 (Glo2). An accumulation of intracellular glyoxal and methylglyoxal leads to protein malfunction and mutation via formation of the advanced glycation end products (AGEs). Studies on mouse behavior suggest that methylglyoxal has anxiolytic properties. In this report, we generated and characterized a mouse knockout for Glo1. The knockout mice were viable without a pronounced phenotypic defect. Increased level of AGEs in Glo1 knockout mice was detected by immunoblotting with anti-MGH1 in liver homogenate, but not in brain. Alterations in behavior were observed in open field, light-dark transition, and tail suspension test. Open field data indicate increased exploration for novel environment and entry/stay in center zone in Glo1 knockout mice. In addition, increased light-dark transition and immobility was observed in the knockout mice. These data indicate that Glo1 knockout reduces anxiety-like behavior, but increases depression like behavior. (C) 2017 Elsevier Inc. All rights reserved.