Current concepts of ethanol dependence.

Alcohol dependence is considered to be divisible into two types (although the divisions between these are indistinct). These are psychological dependence, in which the rewarding effects of alcohol play a primary role, and chemical dependence, in which adaptive changes in the brain initiate punishing effects on withdrawal of alcohol, and suppression of these becomes the primary motive for using the drug. The neurochemical basis for the rewarding effects of alcohol may be the potentiation of GABA at GABAA receptors (causing relaxation) and release of dopamine from mesolimbic neurones (causing euphoria). The adaptive changes which cause the alcohol withdrawal syndrome are not known for certain, but alterations in GABAA receptors, NMDA receptors and voltage-operated calcium channels all have a claim. However, it is distinctly doubtful whether these all contribute to the negatively reinforcing effects of alcohol that are important in chemical dependence, although they may be important in other pathological effects of alcohol abuse. Current research badly needs better communication between basic scientists and clinicians to establish research goals and to improve current models.