Brain Reward Circuits in Alcoholism

Abstract

AbstractThis article discusses the neurocircuitry and the neurochemical systems, as well as the molecular elements within these systems, that are believed to be important in the etiology of alcoholism. Alcoholism is a complex behavioral disorder characterized by excessive consumption of alcohol; a narrowing of the behavioral repertoire toward excessive consumption; the development of tolerance and dependence; and impairment in social and occupational functioning. Animal models of the complete syndrome of alcoholism are difficult if not impossible to achieve, but validated animal models exist for many of the different components of the syndrome.Recent work has begun to define the neurocircuits responsible for the major sources of positive and negative reinforcement that are key to animal models of excessive alcohol intake. Alcohol appears to interact with alcohol-sensitive elements within neuronal membranes that convey the specificity of neurochemical actions. Positive reinforcement appears to be mediated by an activation γ-aminobutyric acid A receptors, release of opioid peptides and dopamine, inhibition of glutamate receptors, and interaction with serotonin systems. These neurocircuits may be altered by chronic alcohol administration. This is reflected by their exhibiting opposite effects during acute alcohol withdrawal, and by the recruitment of other neurotransmitter systems, such as the stress neuropeptide corticotropin-releasing factor. These neuropharmacologic actions are believed to produce allostatic changes in set-point, which set up the vulnerability to relapse that is so characteristic of alcoholism. Future challenges include a focus on understanding exactly how these neuroadaptive changes convey vulnerability to relapse in animals with a history of alcohol dependence.