Methionine enhances alcohol-induced narcosis in mice.

Methionine is an essential amino acid that has been used as a therapeutic drug in some disorders. In this study we questioned whether methionine affects ethanol-induced loss of righting reflex (narcosis). One hour after IP methionine administration (60, 120, 240, 480, 720, 960, and 1280 mg/kg), mice were injected with ethanol (4.0 g/kg), and the duration of loss of righting reflex was recorded. Methionine, at the higher doses (960 and 1280 mg/ kg), significantly increased this effect on ethanol-treated animals. A time-course study revealed that methionine increased the duration of the loss of righting reflex induced by ethanol until 4 h after being injected. Because methionine did not affect blood ethanol levels, no change in peripheral alcohol can explain the observed effects. This potentiation was not specific for ethanol because methionine increased 3-methyl-1-butanol (0.6 g/kg) and 1-propanol (2.4 g/kg)-induced loss of righting reflex as well. Therefore, the results obtained in this study suggest the need for further investigation into methionine-ethanol interactions prior to the use of methionine as an agent that can be used as an antidepressant and to prevent damage to organic tissue in alcoholism.