Dopamine D2 receptors and transporters in type 1 and 2 alcoholics measured with human whole hemisphere autoradiography.

Abstract

Increasing evidence implies the involvement of the dopamine (DA) system in the pathogenesis of alcoholism. We measured striatal DA D(2) receptors in Cloninger type 1 and 2 alcoholics by using [(125)I]epidepride in human postmortem whole hemispheric autoradiography (WHA), which provides high-resolution images corresponding to positron emission tomographic (PET) studies. We also evaluated the correlation between transporter and receptor DA binding site densities and putative correlation of [(125)I]epidepride binding between the dorsal striatum and nucleus accumbens. In the type 1 alcoholics, the DA D(2) receptor density was 21.4-32.6% lower in all dorsal striatal structures (caudate, putamen, globus pallidus) when compared with the controls. Type 2 alcoholics had 19.6-21.4% lower binding in other dorsal striatal structures, except medial globus pallidus, where they were not significantly different from controls. The density of DA D(2) receptors and DAT had a significant positive correlation only in the putamen of type 1 alcoholics. The binding of [(125)I]epidepride showed also consistent and statistically significant positive correlation between nucleus accumbens and all dorsal striatal areas in type 1 alcoholics but not in the controls. In the type 2 alcoholics, the correlation was weaker than that observed in the type 1 alcoholics, and no correlation was observed between nucleus accumbens and globus pallidus. Our results show that these two subgroups of alcoholics have stark differences in their DA D(2) receptor binding characteristics. Type 2 alcoholics may have selective deficiency in the dorsal striatum, whereas in limbic structures they may not differ significantly from controls. Moreover, WHA provides a useful tool for detailed mapping of neuronal receptors in healthy as well as diseased brain, and can also be used in radioligand development for PET.