Postnatal development of dopamine D₁-like (D₁/D₅) receptors in rat caudate-putamen (CPu), nucleus accumbens (NAc), hippocampus, frontal and entorhinal cerebral cortex was assessed between postnatal days (PD) 7–60 by in vitro receptor autoradiography. Density of [³H]SCH-23390 binding to D₁-like receptors increased from PD-7 to a peak at PD-28 in CPu (11-fold) and NAc (23-fold), then declined by 20–40% in both regions over PD-35–60, to adult levels. In hippocampus, frontal and entorhinal cortex, D₁-like receptors increased by lesser amounts (3- to 4-fold) from PD-7 to stable, maximal adult levels at PD-60. Evidently, excess D₁-like receptors were eliminated during maturation of CPu and NAc, but not in the other forebrain regions. Postnatal D₁-like receptor development in rat forebrain paralleled that of D₂- and D₄-like receptors in the same regions.

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