Background: Glyoxalase 1 (GLO1) is an enzyme that metabolizes the glycolytic byproduct methylglyoxal (MG), which is a competitive partial agonist at GABAA receptors.Pharmacological inhibition of GLO1 increases concentrations of MG in the brain and decreases binge-like ethanol drinking. The present study assessed whether pharmacological inhibition of GLO1, or genetic over expression of Glo1, would also alter the locomotor effects of ethanol, which might explain reduced ethanol consumption following GLO1 inhibition. We used the prototypical GABAA receptor agonist muscimol as a positive control.Methods: Male C57BL/6J mice were pretreated with a single dose of either the GLO1 inhibitor S-bromobenzylglutathione cyclopentyl diester (pBBG; 7.5 mg/kg; Experiment 1) or muscimol (0.75 mg/kg; Experiment 2), or their corresponding vehicle. We then determined whether the locomotor response to a range of ethanol doses (0, 0.5, 1.0, 1.5, 2.0, and 2.5) was altered by either pBBG or muscimol pretreatment. We also examined the locomotor response to a range of ethanol doses in FVB/NJ wild type and transgenic Glo1 over expressing mice (Experiment 3).We also assessed anxiety-like behavior as measured by time spent in the center of an open field in all three experiments.
Results:The ethanol dose-response curve was not altered by pretreatment with pBBG or by transgenic overexpression of Glo1. In contrast, muscimol blunted locomotor stimulation at low ethanol doses, and potentiated locomotor sedation at higher ethanol doses.
Conclusions:The dose of pBBG used in this study has been previously shown to reduce ethanol drinking. Glo1 overexpression has been previously shown to increase ethanol drinking.However, neither manipulation altered the dose response curve for ethanol's locomotor effects, whereas muscimol appeared to enhance the locomotor sedative effects of ethanol. The present ! 2 data demonstrate that reduced ethanol drinking caused by GLO1 inhibition is not due to potentiation of ethanol's stimulant or depressant effects.