The most prominent effects of alcohol involve stimulation of the gamma amino butyric acid (GABA) neurotransmitter system, which accounts for many of the sedative and other effects. As with other drugs of abuse, there is release of dopamine in the nucleus accumbens that relates to the rewarding effects of alcohol. Alcohol also activates aspects of the opioidergic system and it affects the hypothalamic pituitary adrenal system (HPA) and other neuropeptide systems. Alcohol acts to inhibit glutamatergic function. During chronic alcohol exposure there is down regulation of the GABA system and up regulation of the glutamatergic system and so that during alcohol withdrawal there is impaired inhibition and excessive excitation, which can account for the observed alcohol withdrawal symptoms.Stress increases voluntary alcohol intake and corticotrophin-releasing hormone (CRH) antagonists reduce alcohol intake following stress and during alcohol withdrawal.