Cortical dopamine D2 receptors in type 1 and 2 alcoholics measured with human whole hemisphere autoradiography

Alcoholism has been associated with lower density of striatal dopamine (DA) D(2) receptors, but there is much less data on cortical DA D(2) receptors. We evaluated the [(125)I]epidepride binding to DA D(2) receptors in Cloninger type 1 and 2 alcoholics and controls in frontal, temporal, and anterior cingulate cortices by using human postmortem whole hemispheric autoradiography, which provides high-resolution images corresponding to positron emission tomographic (PET) studies. Type 1 alcoholics had lower and type 2 alcoholics had higher DA D(2) receptor density in all cortical areas compared to controls. Although the results did not reach statistical significance, the effect sizes were high. The DA D(2) receptor density in type 2 alcoholics decreased statistically significantly with age, and after correcting for age the binding values also fell below the level of controls. A statistically non-significant tendency towards a decrease of cortical DA D(2) receptors was seen in controls, whereas in the type 1 alcoholic group no consistent correlation or even tendency towards increase with age was observed. Our results give preliminary evidence that DA D(2) receptors in cortical areas may be lower among both groups of alcoholics, but not necessarily of same magnitude as in subcortical structures. The rapid decline of cortical DA D(2) receptors among type 2 alcoholics may have some relevance to their antisociality, because this trait tends to diminish with age. The absence of correlation or even tendency towards increase of cortical DA D(2) receptors with age seen in type 1 alcoholics may give further evidence that they have a pre-existing dopaminergic deficit. However, these results especially regarding aging effect must be considered as preliminary due to the different age-range of type 2 alcoholics compared to two other groups.