Alcohol and dopamine

Abstract

Dopamine is a neuromodulator that is used by neurons in several brain regions involved in motivation and reinforcement, most importantly the nucleus accumbens (NAc). Dopamine alters the sensitivity of its target neurons to other neurotransmitters, particularly glutamate. In addition, dopamine can affect the neurotransmitter release by the target neurons. Dopamine-containing neurons in the NAc are activated by motivational stimuli, which encourage a person to perform or repeat a behavior. Even low alcohol doses can increase dopamine release in part of the NAc. This dopamine release may contribute to the rewarding effects of alcohol and may thereby play a role in promoting alcohol consumption. In contrast to other stimuli, alcohol-related stimuli maintain their motivational significance even after repeated alcohol administration, which may contribute to the craving for alcohol observed in alcoholics.

Figure 1

Schematic representation of the major dopaminergic systems (viewed from the top of the head). The nigrostriatal system originates in the A9 cell group and extends to the dorsal striatum, which includes the caudate nucleus and putamen (CPU). The mesolimbic system originates primarily in the A10 cell group and extends to the ventral striatum, which includes the nucleus accumbens (NAc) and the olfactory tubercle (OT). The mesocortical system also originates primarily in the A10 cell group and affects various regions of the cerebral cortex. SOURCE: Adapted with permission from Di Chiara, G. In vivo brain dialysis of neurotransmitters. Trends in Pharmacological Sciences 11:116–121, 1990.

Figure 2

Key areas of the brain (e.g., striatum and extended amygdala) with dopaminergic transition (viewed in a cross-section of the left hemisphere of the brain). The striatum includes the caudate nucleus and putamen (CPU) (dark blue) as well as the nucleus accumbens core (yellow) and shell (red). The extended amygdala is distinguished into a central division (red) and a medial division (light blue). The central division includes the nucleus accumbens shell, the lateral part of the bed nucleus of stria terminalis (BSTL), the central amygdala (CE), and other neuronal groups bridging these areas (IPAC). From these structures, neurons extend to the lateral hypothalamus (LH), visceral nuclei in the brain stem (MPT), and medulla. The medial division of the extended amygdala includes the medial part of the bed nucleus of stria terminalis (BSTM), the medial amygdala (ME), and other associated neuronal groups. Neurons originating in the medial division extend to the medial hypothalamus (MH). SOURCE: Adapted with permission from Heimer et al. 1997.