Evidence for a fast receptor turnover of D1 dopamine receptors in various forebrain regions of the rat.

The time course for recovery of binding of the D1 dopamine receptor antagonist radioligand [3H]SCH 23390, after administration of the irreversible antagonist N-ethoxycarbonyl-2-ethoxy-1,2-dihydroquinoline (EEDQ), was studied in the neostriatum, nucleus accumbens, tuberculum olfactorium and claustrum of the rat by means of quantitative receptor autoradiography. The results showed that the receptor degradation rate constant (k) ranged from 0.0163 to 0.0315 h-1 and that the receptor production rate (r) ranged from 8.52 to 24.96 fmol/mg protein/h. These results indicate that the D1 receptor has a considerably faster turnover than the D2 receptor, which suggests that the D1 receptor may require a dynamic regulation including also changes in receptor production and degradation rates.