The role of serotonin in alcohol use and abuse

Alcohol is a widely used and abused psychoactive drug in Western societies. Long-term consumption may lead to alcohol addiction, a severe psychiatric disorder. The serotonergic system of the brain is a key regulator of reinforcement learning and behavioral plasticity and has long been considered as an important mediator of alcohol-related physiological and behavioral adaptations. In this chapter we review the action of alcohol on the serotonergic system, and how components of the system contribute to the establishment and expression of alcohol consumption, alcohol instrumentalization and alcohol addiction-related behaviors in animal models and in humans. Altogether, accumulating evidence suggests that a prominent activation of the serotonergic system after alcohol exposure is reversed after chronic alcohol consumption. The serotonergic system contributes essentially to the establishment of controlled alcohol consumption and may also be involved in distinct ways of alcohol instrumentalization. Long-term adaptations after chronic alcohol consumption in the serotonergic system may contribute to the transition from controlled to compulsive consumption and addiction. Although no serotonin-based pharmacotherapy for alcohol addiction has emerged yet, serotonin receptors still offer interesting targets for potential therapeutic approaches.