DIFFERENTIAL EXPRESSION OF D1 AND D5 DOPAMINE-RECEPTORS IN THE FETAL PRIMATE CEREBRAL WALL

Previous film autoradiographic studies demonstrated that, during corti cogenesis, dopamine receptors of the D1 class are abundant in the embr yonic primate cerebral wall. In the present study, we expand these fin dings by identifying the cellular elements of the fetal occipital cere bral wall expressing D1 and D5 subtypes of the D1 dopamine receptor cl ass. We have examined tissue from monkey fetuses collected at 70, 90 a nd 120 days of gestation using antibodies directed against C-termini o f the D1 and D5 dopamine receptors. At all three embryonic ages studie d, we found D1 and D5 receptors expressed by multiple cell types of th e embryonic cerebral wall. Both D1 and D5 receptor proteins are produc ed by pyramidal neurons of the cortical plate and by a variety of inte rstitial neurons of the subplate and intermediate zones. D1 and D5 rec eptors are also present in cells of the proliferative ventricular and subventricular zones, some of which were identified as dividing cells. In addition, D1 and D5 receptors are detectable in the protoplasmic a stroglial and ependymal cells distinguishable in monkey fetuses collec ted at 120 days of gestation. Some cellular elements of the embryonic monkey cerebral wall express only one subtype of the D1 dopamine recep tor class. For example, embryonic Cajal-Retzius neurons in the margina l zone and migrating neurons in the intermediate zone are immunoreacti ve only to D5 antisera. In contrast, radial glia can be labeled only w ith D1 receptor-specific antisera. Finally, only D1 receptors are dete ctable in the blood vessels penetrating the embryonic monkey cerebral wall. Based on these observations, we propose that dopamine receptors of the D1 class play an important role in regulating cerebral cortical formation and that D1 and D5 receptor subtypes may participate in reg ulation of different aspects of this process.