Age-dependent decline in human brain dopamine D1 and D2 receptors.

Dopamine D1 and D2 receptor binding was investigated in the caudate nucleus and putamen in 65 individuals ranging from 6 to 93 years of age. [3H]SCH 23390 and [3H]spiroperidol were used as ligands for D1 and D2 receptors, respectively. A full Scatchard analysis with several ligand concentrations was performed yielding Bmax and Kd values. The number of D1 and D2 receptors declined with age both in the caudate nucleus and putamen without any change in the mean dissociation constant. The ratio of D1:D2 receptors remained unchanged. The results show that the dopaminergic system degenerates in the aging striatum and may contribute to the frequent occurrence of extrapyramidal symptoms in the elderly.