D-1-DOPAMINERGIC AND D-2-DOPAMINERGIC RECEPTORS IN THE DEVELOPING CEREBRAL-CORTEX OF MACAQUE MONKEY - A FILM AUTORADIOGRAPHIC STUDY

Film autoradiography was used to study the distribution of D-1- and D-2-dopaminergic receptors in the prefrontal association, somatosensory, primary motor and visual regions in the developing cerebral cortex of macaque monkeys. D-1 receptors were labeled with [I-125]SCH23982, while D-2 sites were visualized with [I-125]epidepride. D-1- and D-2-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 D-1 and D-2 receptors have different distributions, during development there are substantial similarities in the laminar patterns of these sites. In particular, both D-1 and D-2 receptors tend to concentrate in the marginal zone and layer V of the developing cortical plate. The autoradiograms also show a high density of D-1-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 ih the proliferative zones and fast maturation of the laminar distribution suggests that dopaminergic receptors may be involved in the regulation of cortical development.