Aggression and repeated alcohol drinking-in-the-dark: dissecting subtypes in outbred mice.

RATIONALE: Repeated bouts of alcohol consumption increase the risk for developing alcohol use disorders and influence social dynamics, including aggression. Intermittent, weekly binge-like drinking-in-the-dark (DID) can escalate such intake in mice, potentially altering the trajectory of adaptive social behaviors.

OBJECTIVE

To examine individual patterns of alcohol intake over repeated weeks of DID with corresponding measures of offensive aggression in outbred Swiss Webster (CFW) resident mice.

METHODS

CFW resident male mice were given 2 h of access to either water or 16% ethanol (w/v) for three days, followed by 4 h of access on day four. This DID protocol was implemented over nine consecutive weeks. Offensive aggression was assessed throughout the experiment, with aggression tests occurring in a neutral arena 20 h after the cessation of the weekly 4-h access session while mice were no longer intoxicated. Measures of total alcohol intake (i.e., g/kg) and the frequency of attacks (i.e., biting), were collected over each week. Intake patterns were subsequently visualized using Gaussian mixture modeling.

RESULTS

A subset of CFW mice significantly escalate their alcohol intake across weeks, with group means reaching ~ 4 g/kg in 4 h by Week 9. Offensive aggression appears to be maintained in higher alcohol-drinkers relative to lower alcohol-drinkers.

CONCLUSION

Repeated bouts of drinking and aggression testing in outbred mice reveal individual differences in alcohol intake that align with individual differences in aggression. Such trait-like differences reveal a subset of individuals with a vulnerability to consume more alcohol and to engage in offensive aggression while not intoxicated.