Development of β₁ and β₂ adrenergic receptors in baboon brain: An autoradiographic study using [¹²⁵I]iodocyanopindolol

[¹²⁵I]iodocyanopindolol (ICYP) autoradiography was used to investigate the temporal development and distribution of β₁ and beta;₂ receptors in brains of baboons at ages embryonic day 100 (E100), full‐term gestation (E180), and 3 years. In all brain regions examined, with the exception of the hippocampus, binding to β₁ receptors exceeded that to β₂ receptors. The highest densities of ββ₁ receptors were found in the caudate nucleus, putamen, globus pallidus, substantia nigra, and cerebral cortex; intermediate receptor densities were observed in most nuclei of thalamus, and the lowest concentrations were in the hippocampus. At E100, β₁ receptors were identified in the striatum, globus pallidus, and thalamus. During maturation, the number of β₁ receptors declined in cortical areas but increased in the head of the caudate and putamen. Significant differences in the developmental distribution of β₁ receptors during development were also detected: at E100 and E180 β₁ receptors appeared as patches in the caudate and putamen, but by 3 years of age they were more homogeneously distributed in both regions; changes also occurred in the distribution of binding within cortical layers. Autoradiograms of [¹²⁵I]ICYP and [³H]mazindol binding show overlapping patches of labeling in the E180 striatum, suggesting a possible developmental association between β receptors and dopamine high‐affinity uptake carrier sites. This study demonstrates that noradrenergic receptors in the primate forebrain undergo significant developmental reorganization with regional variations.