Cortical dopamine D₁ receptors in type 1 and type 2 alcoholics measured with human whole hemisphere autoradiography

Abstract 

A large body of evidence indicates the importance of dopamine (DA) activation for ethanol reinforcement, and animal models of alcoholism have implied the involvement of DA D₁ receptors in this context. We studied cortical DA D₁ receptors in nine type 1 alcoholics (late-onset, binge-drinker), eight type 2 alcoholics (early-onset, antisocial) and 10 controls by using [³H]SCH23390 as a radioligand in postmortem human whole hemisphere autoradiography. We also evaluated correlations of DA D₁ receptors between the cortical and subcortical areas and between cortical DA transporters and DA D₂ and D₃ receptors by comparing the present results to our earlier studies. On the average, type 2 alcoholics were younger and had more violent causes of death than type 1 alcoholics and controls. There were no statistically significant differences between the groups, suggesting that cortical DA D₁ receptors do not play a major role in alcoholism. However, among type 2 alcoholics, the binding was consistently lower (8.6%–22.3%) than among controls, and the effect sizes showed a large effect in the anterior cingulate (0.90) and frontal (0.87) cortices. Interestingly, among type 2 alcoholics, the correlation of DA D₁ receptors between two ventral midbrain structures (substantia nigra and amygdala) and anterior cingulate cortex was significantly negative, whereas in the type 1 alcoholics and controls, the correlations were significantly positive.

Keywords: Alcohol-induced disorders, Brain, Nucleus accumbens, Substantia nigra, Amygdala, Nervous system diseases