Trait sensitivity to positive feedback is a predisposing factor for several aspects of compulsive alcohol drinking in male rats: behavioural, physiological, and molecular correlates.

Alcohol use disorder (AUD) is one of the most common psychiatric disorders and a leading cause of mortality worldwide. While the pathophysiology underlying AUD is relatively well known, the cognitive mechanisms of an individual's susceptibility to the development of alcohol dependence remain poorly understood. In this study, we investigated the theoretical claim that sensitivity to positive feedback (PF), as a stable and enduring behavioural trait, can predict individual susceptibility to the acquisition and maintenance of alcohol-seeking behaviour in rats. Trait sensitivity to PF was assessed using a series of probabilistic reversal learning tests. The escalation of alcohol intake in rats was achieved by applying a mix of intermittent free access and instrumental paradigms of alcohol drinking. The next steps included testing the influence of sensitivity to PF on the acquisition of compulsive alcohol-seeking behaviour in the seeking-taking punishment task, measuring motivation to seek alcohol, and comparing the speed of extinction and reinstatement of alcohol-seeking after a period of abstinence between rats expressing trait insensitivity and sensitivity to PF. Finally, trait differences in the level of stress hormones and in the expression of genes and proteins in several brain regions of interest were measured to identify potential physiological and neuromolecular mechanisms of the observed interactions. We showed that trait sensitivity to PF in rats determines the level of motivation to seek alcohol following the experience of its negative consequences. They also revealed significant differences between animals classified as insensitive and sensitive to PF in their propensity to reinstate alcohol-seeking behaviours after a period of forced abstinence. The abovementioned effects were accompanied by differences in blood levels of stress hormones and differences in the cortical and subcortical expression of genes and proteins related to dopaminergic, serotonergic, and GABAergic neurotransmission. Trait sensitivity to PF can determine the trajectory of alcohol addiction in rats. This effect is, at least partially, mediated via distributed physiological and molecular changes within cortical and subcortical regions of the brain.