D1- and D2 dopaminergic receptors in the developing cerebral cortex of macaque monkey: a film autoradiographic study.

Film autoradiography was used to study the distribution of D1- and D2-dopaminergic receptors in the prefrontal association, somatosensory, primary motor and visual regions in the developing cerebral cortex of macaque monkeys. D1 receptors were labeled with [125I]SCH23982, while D2 sites were visualized with [125I]epidepride. D1- and D2-dopaminergic sites are already present in all cortical areas at embryonic day 73, the earliest age observed in this study. In contrast to the adult cortex, where D1 and D2 receptors have different distributions, during development there are substantial similarities in the laminar patterns of these sites. In particular, both D1 and D2 receptors tend to concentrate in the marginal zone and layer V of the developing cortical plate. The autoradiograms also show a high density of D1-dopaminergic sites in the transient ventricular and subventricular zones, where cortical neurons are generated. Although there is a significant rearrangement of the early laminar patterns, the adult distribution of both dopaminergic receptors in most cortical areas is achieved prenatally, soon after all cortical neurons assume their final positions. An early presence in the cerebral wall, a high density in the proliferative zones and fast maturation of the laminar distribution suggests that dopaminergic receptors may be involved in the regulation of cortical development.