et al., 1993). VAR also releases DA in the NAc during the first hour following central administration, though to a lesser degree than does alcohol, and continues to stimulate DA release for several hours following administration (Ericson et al., 2009). However, interestingly, co-administration of VAR and alcohol into the NAc at the same time inhibits alcohol-induced DA release (Ericson et al., 2009). It is not known whether the ability of VAR to reduce alcohol intake is due to the fact that VAR blocks alcohol-induced DA release during the first hour of brain exposure to alcohol, thus reducing alcohol-induced euphoria and reducing the motivation to drink, or whether the VAR-induced stimulation of DA release at later time intervals acts through a “drug substitution” mechanism to reduce alcohol withdrawal symptoms and craving, and hence the motivation for alcohol drinking. Both of these explanations may be correct depending on the stage of the addiction process being examined since early alcohol drinking, in nonaddicted individuals, is thought to be reinforced by alcohol-induced euphoria while alcohol drinking in alcohol-dependent individuals is thought to be reinforced by alcohol-induced attenuation of withdrawal symptoms and craving.
