Striatal D2 dopamine receptor characteristics of nine male patients with alcohol dependence abstinent for 1-68 weeks and eight healthy male volunteers were studied in vivo with positron emission tomography. The selective D2 receptor ligand [11C]raclopride and equilibrium model was used for D2 receptor density (Bmax) and affinity (Kd) measurements. A trend for a decreased striatal D2 receptor density and for reduced D2 receptor affinity was observed in patients with alcohol dependence. These parameters were not statistically significantly different between alcoholics and controls, but the ratio between D2 receptor density and affinity (Bmax/Kd or the striatum/cerebellum ratio from the high specific activity scan) was highly significantly lower in alcoholics than that of controls. In conclusion, the low D2 dopamine receptor Bmax/Kd ratio (striatum/cerebellum ratio) indicates that specific aspects of striatal [11C]raclopride binding in vivo are deviant in alcoholics compared to controls. The result is compatible with a reduced avidity of striatal dopamine D2 receptors in alcoholics, which is in line with the idea that D2 dopaminergic mechanisms are involved in the biology of alcohol dependence in man.

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