Intraventricular administration of BDNF increases the number of newly generated neurons in the adult olfactory bulb

Abstract

We have previously demonstrated that the most rostral part of the subventricular zone (SVZ) is a source of neuronal progenitor cells whose progeny are destined to become interneurons of the olfactory bulb. To determine whether the number of newly generated neurons in the adult olfactory bulb could be increased by the administration of an exogenous factor, brain-derived neurotrophic factor (BDNF) was infused for 12 days into the right lateral ventricle of adult rat brains. The production of new cells was monitored by either the intraventricular infusion or intraperitoneal injection of the cell proliferation marker BrdU. In both experimental paradigms we observed significantly more BrdU-labeled cells in the olfactory bulbs on the BDNF-infused side than in the olfactory bulb of PBS-infused animals. Analysis of the BDNF-infused brains of animals injected intraperitoneally with BrdU demonstrated a 100% increase in the number of BrdU-labeled cells in the bulb, the preponderance ( approximately 90%) of which were double-labeled with a neuron-specific antibody. These results demonstrate that the generation and/or survival of new neurons in the adult brain can be increased substantially by an exogenous factor. Furthermore, the SVZ, and in particular the rostral part, may constitute a reserve pool of progenitor cells available for neuronal replacement in the diseased or damaged brain.