Ethanol as a reinforcer for rats: factors of facilitation and constraint.

This review examines some particular approaches that have been used to investigate factors that facilitate or constrain the self-administration of ethanol by rats. A technique for increasing ethanol self-administration in rats, the prandial drinking method, was examined and the effect of body-weight reduction on drug intake was discussed. Emphasis was placed on how ethanol intake may be controlled by processes in addition to the direct pharmacological actions of the drug in the CNS. These processes may be physiological. Evidence was presented for a relationship between activity in the renin-angiotensin system and the self-administration of ethanol. These processes may also be environmental. Using the place-conditioning technique, demonstrations were presented of how the context or situation in which ethanol is experienced may determine whether preference or aversion for the drug develops. Such a diversity in the factors that can potentially control ethanol intake may complicate the identification of the causes of alcohol abuse, but this same diversity also holds out greater hope that manipulations may be found to reduce excessive drinking in humans.