l-Cysteine, a thiol amino acid, increases the stimulating acute effect of ethanol on locomotion

Abstract 

The present study deals with the effect of l-cysteine on the acute stimulating effects of ethanol. Swiss albino mice were pretreated with 0.0, 18.75, 37.50, or 75.00 mg/kg of cysteine simultaneously, 30 or 60 min, before the administration of saline or 0.8, 1.6, 2.4, or 3.2 g/kg of ethanol at 20% vol./vol. After these treatments, mice were left in the open-field chamber for 20 min, and locomotor activity was evaluated for the last 10 min. The specificity of the effects of l-cysteine was analyzed with the use of two drugs that also induce locomotor activity—d-amphetamine and methanol. Mice received l-cysteine (37.5 mg/kg), and 30 min after this treatment d-amphetamine (2 mg/kg) or methanol (2.4 g/kg) was injected. Data showed that l-cysteine at 37.5 mg/kg was able to increase locomotion induced by 2.4 and 3.2 g/kg of ethanol when it was administered 30 min before ethanol injection. The effects of l-cysteine are specific for the stimulation of ethanol on locomotion, because l-cysteine does not alter d-amphetamine-induced locomotor activity or methanol-induced locomotion. Moreover, blood ethanol levels were not affected by l-cysteine pretreatment. Therefore, the present findings demonstrated that ethanol-induced locomotor effects are enhanced by l-cysteine, in a manner similar to that of other sulfur amino acids.

Keywords:  Ethanol, l-Cysteine, Acetaldehyde, Mice, Locomotion, Blood ethanol levels, Methanol, d-Amphetamine