DOPAMINERGIC AND GABAERGIC INTERNEURONS OF THE OLFACTORY-BULB ARE DERIVED FROM THE NEONATAL SUBVENTRICULAR ZONE

Earlier studies in our laboratory have demonstrated that a discrete re gion of the anterior part of the neonatal subventricular zone (SVZa) c ontains exclusively neuronal progenitor cells. The descendants of the SVZa progenitor cells are destined for the granule cell and glomerular layers of the olfactory bulb, where they differentiate into granule a nd periglomerular cells, the interneurons of the olfactory bulb, respe ctively. In the present set of experiments we examined the neurotransm itter phenotype of the SVZa-derived cells. In order to label SVZa-deri ved cells, the cell proliferation marker bromodeoxyuridine (BrdU) was injected into the SVZa of postnatal day 2 (P2) rats. After 3 weeks, by which time most of the SVZa-derived cells have migrated to their fina l destination in the bulb, the animals were perfused and their brains processed for immunohistochemistry. To identify the neurotransmitter p henotype of the SVZa-derived cells, sagittal sections of the forebrain , including the olfactory bulb, were double-labeled with an antibody t o BrdU in conjunction with an antibody to gamma-amino-butyric acid (GA BA) or tyrosine hydroxylase (TH), the rate limiting enzyme in the synt hesis of dopamine. Using simultaneous indirect immunofluorescence to d etect the presence of single- and double-labeled cells, we found that 59% and 51% of the BrdU-positive cells were immunoreactive for GABA in -the granule cell and glomerular layers, respectively. In addition, 10 % of the BrdU-positive periglomerular cells were immunoreactive for TH . The presence of double-labeled (BrdU-positive/GABA-positive and BrdU -positive/TH-positive) cells in the olfactory bulb, demonstrates that the SVZa is a source of the GABAergic and dopaminergic interneurons of the olfactory bulb during postnatal development. Copyright (C) 1996 I SDN.