Does caffeine alter preference or patterns of voluntary ethanol consumption in Swiss male mice?

The co-consumption of alcohol (ethanol) and caffeine, commonly found in alcoholic beverages mixed with energy drinks (AmED), has been linked to increased alcohol intake and heightened risk-taking behaviors. However, the effects of this combination under voluntary drinking conditions in animal models remain poorly understood. The present study investigated whether caffeine modulates ethanol intake in Swiss male mice, an outbred strain with inherent low ethanol preference. Mice were exposed to a two-bottle choice Intermittent Overnight Drinking (IOD) protocol for 12 sessions. Each mouse had access to water and either ethanol (10%), caffeine (0.75 mg/mL), or a combination of both. Using lickometer devices, we analyzed drinking microstructure, including total intake, latency to first lick and bout, and temporal licking patterns. Caffeine and water were consumed in similar amounts and followed comparable circadian patterns, whereas both ethanol and ethanol + caffeine solutions were consistently avoided. Thus, in Swiss male mice, caffeine did not modify ethanol intake. These findings emphasize the importance of strain-specific studies for a better understanding of the behavioral interaction between alcohol and caffeine.