Habitual Ethanol Seeking and Licking Microstructure of Enhanced Ethanol Self-Administration in Ethanol-Dependent Mice

A significant component of ethanol (EtOH) dependence is the disruption to decision-making processes. Prior work has shown EtOH dependence biases habitual seeking of EtOH and disrupts neural mechanisms supporting decision-making. This has contributed to the hypothesis that habitual EtOH seeking in EtOH dependence may promote excessive habitual or compulsive EtOH consumption. However, decision-making and behavioral processes underlying seeking and consummatory behaviors differ. Here, we examine the microstructure of EtOH consummatory behavior in the context of habitual EtOH seeking.

Following home cage pre-exposure to EtOH, C57Bl/6J mice underwent 4 rounds of chronic intermittent EtOH (CIE) or air exposure. Following acute withdrawal, mice began training for operant self-administration of 15% EtOH. Training consisted of 16-hour sessions in which mice were trained in a random ratio (RR) schedule of reinforcement for 30-second access to the EtOH sipper. To test for CIE-induced changes in action control, we used sensory-specific satiation and assessed the effect of outcome devaluation on EtOH seeking. Importantly, the use of a lickometer during operant training allowed us to measure the microstructure of lick behavior.

Prior induction of EtOH dependence led to increased EtOH seeking, consumption, and an insensitivity to outcome devaluation, the latter indicative of habitual EtOH seeking. We also found altered consummatory lick patterns in CIE-exposed mice compared to Air controls. While CIE mice had significantly more licks in a burst and a longer burst duration, there were no differences in the total number of bursts compared to Air controls. Furthermore, these EtOH consummatory behaviors correlated with blood EtOH concentrations (BECs), while EtOH-seeking responses did not.

Our results confirm that EtOH dependence can produce habitual EtOH seeking and suggests the increased EtOH consummatory behaviors following EtOH dependence are separable from decision-making processes controlling EtOH seeking.