ALPHA-2A-ADRENERGIC RECEPTORS ARE EXPRESSED BY DIVERSE CELL-TYPES IN THE FETAL PRIMATE CEREBRAL WALL

The cellular elements of the fetal monkey cerebral wall expressing alp ha 2A, the most common subtype of the alpha 2 receptor class, were exa mined by using nonisotopic in situ hybridization and immunohistochemis try with double-labeling for cell type-specific markers. At the three embryonic ages examined, E70, E90, and E120, alpha 2A receptors were e xpressed throughout the embryonic cerebral wall. In the E70 and E90 fe tuses, alpha 2A receptors were observed in most cells of the prolifera tive zones. Some alpha 2A-positive cells also expressed a proliferatio n-associated antigen, Ki-67, suggesting that the receptors are present in dividing cells. Furthermore, at E90, alpha 2A receptors were detec ted on fibers passing between the ventricular and subventricular proli ferative zones. At all ages studied, alpha 2A receptors were expressed by migrating neurons in the intermediate zone, characterized by a spi ndle-like shape, radial alignment, and close association with radial g lia. alpha 2A receptors were also expressed by postmigrational microtu bule-associated protein-2-positive neurons of the intermediate and sub plate zones and the cortical plate. In the marginal zone, alpha 2A rec eptors were present in the Cajal-Retzius neurons. Finally, alpha 2A re ceptors were seen in the glial fibrillary acidic protein-positive cell s at all ages studied. In addition, dopamine-beta-hydroxylase immunohi stochemistry, employed to determine the potential source of noradrenal ine in the embryonic cerebral wall, revealed noradrenergic innervation in the marginal, subplate, and intermediate zones of the monkey occip ital lobe as early as E70. Based on our observations and available dat a on alpha 2A signal transduction pathways, we propose that these rece ptors are involved in regulating the generation, migration, and matura tion of cerebral cortical cells. (C) 1997 Wiley-Liss, Inc.