Low, but not moderate, caffeine increases alcohol intake in male and female C57 mice

Abstract

Caffeine and alcohol are two of the most popular and legal drugs around the world. In America, both drugs are easily accessible, and this has led to the two drugs being used in frequent combination with one another. Previous studies have revealed much about the mechanisms of each drug, but the effects of co-consumption are not yet fully understood. The two drugs appear to have opposing effects, as caffeine is a stimulant and alcohol is a depressant, but more research is needed on their effects when combined. One main concern is that caffeine could reduce how intoxicated a person feels, leading to increased alcohol consumption or other risky behaviors. Mice have previously been used to study alcohol, caffeine, and their combination. This previous research is not conclusive, but does suggest the potential for dose-dependent effects of caffeine when combined with alcohol. This experiment intended to compare the consumption rates of caffeine and alcohol and to observe the withdrawal effects of these two drugs. Specifically, varying levels of caffeine and alcohol were examined to see if the effects of the combination is dependent upon dose. C57BL/6J mice (n=48) were provided with caffeine (0.015% or 0.03%) and/or alcohol (3-20%) in a two-bottle intermittent access voluntary paradigm. Fluid consumption was recorded daily for five weeks and mice were then individually tested in an elevated plus maze (EPM) to assess anxiety-like behaviors during withdrawal. Although small amounts of caffeine alone were consumed throughout the study, the amount of alcohol consumed steadily increased until the highest concentration (20%) was presented. Both sexes consumed the most alcohol when it was paired with the lower dose of caffeine (0.015%) compared to either alcohol alone or alcohol in combination with the higher dose of caffeine (0.03%) and consumed more caffeine at each concentration when it was paired with alcohol. Overall, less consistent consumption patterns were observed in female mice. The results from the EPM revealed no significant difference between experimental groups and no differences between male and female mice. These results suggest that a specific amount of caffeine may be necessary to impact alcohol consumption in mice. More research is necessary to determine the psychological effects of withdrawal from these drugs.