Neurobehavioral studies of ethanol reward and activation.

Although generally considered to be a depressant drug, ethanol has both stimulant and depressant effects on behavior. This biphasic action of ethanol may be related to its reinforcing effects and to the neurobehavioral events that occur with changes in blood alcohol concentration (BAC). Ethanol was found to reduce the threshold and increase response rates for brain stimulation reward (BSR) at lateral hypothalamic, but not ventral noradrenergic bundle brain sites. These effects were also found to only occur when testing occurred on the ascending limb of the BAC. Studies of the effects of ethanol on open-field activity showed that the stimulant effects of low doses of ethanol were also seen only during the ascending limb of the BAC; depression was usually found during the descending limb. Neurochemical data from other investigators suggest that the facilitation of BSR and stimulation of activity may be mediated by mesolimbic dopamine systems.