Neurogenesis in the subventricular zone and rostral migratory stream of the neonatal and adult primate forebrain

Throughout life, the anterior part of the postnatal rodent subventricular z one (SVZa), surrounding the lateral ventricles, contains a prolific source of neuronal progenitor cells that retain their capacity to concurrently gen erate neurons and migrate along the rostral migratory stream (RMS) to the o lfactory bulb, where they differentiate into interneurons. This study was d esigned to determine whether the SVZ and RMS of the postnatal primate also harbor a specialized population of neuronal progenitors with the capacity t o divide while they migrate. In order to reveal the spatial-temporal change s in the distribution and composition of the neuronal progenitor cells in t he primate SVZ and RMS, seven rhesus monkeys, ranging in age from 2 days to 8 years, were given a single injection of the cell proliferation marker br omodeoxyuridine (BrdU) 3 h before they were perfused. The phenotypic identi ty of the BrdU(+) cells was revealed by double labeling sagittal sections w ith cell type-specific markers. From birth onward the distribution of BrdU( +) cells with a neuronal phenotype is extensive and largely overlapping wit h that of the rodent. Similar to the rodent brain the neuronal progenitors are most numerous in neonates. The BrdU(+) neurons in the primate forebrain extend lateral and ventral to the lateral ventricle and all along the RMS. The cytoarchitectonic arrangement and appearance of the neuronal progenito r cells is quite varied in the primate compared to the rodent; in some loca tions the cells are aligned in parallel arrays resembling the neuronal chai ns of the adult rodent RMS, whereas in other positions the cells have a hom ogeneous "honeycomb" arrangement. The chains are progressively more pervasi ve in older primates. Akin to the RMS of adult rodents, in the primate SVZ and RMS the astrocytes often form long tubes enveloping the chains of neuro nal progenitors. Our study demonstrates that the primate forebrain, similar to the rodent forebrain, harbors a specialized population of mitotically a ctive neuronal progenitor cells that undergo extensive rearrangements while continuing to proliferate throughout life. (C) 2001 Academic Press.