Functional Convergence Of Neurons Generated In The Developing And Adult Hippocampus

DIEGO A. LAPLAGNE; MARIA SOLEDAD ESPOSITO; VERONICA C. PIATTI; NICOLAS A. MORGENSTERN; CHUNMEI ZHAO; HENRIETTE VAN PRAAG; FRED. H. GAGE; ALEJANDRO F. SCHINDER

Viena

Congreso; 5th Fens Forum of Neuroscience; 2006

Fens Forum of Neuroscience

The dentate gyrus (DG) of the hippocampus generates principal neurons throughout life. The physiological role of these adult-born neurons is a subject of intense research and debate. Two possible scenarios are compatible with current knowledge: 1) neurons generated in the adult DG possess unique functional properties such as different excitability, connectivity or plasticity when compared to neurons born during development; 2) all neurons in the adult DG mature into a similar phenotype, which becomes independent of their time of birth. In the first case, at least two different neuronal populations coexist in the DG. In the latter case, all neurons belong to the same functional population and continuous neuronal replacement acts as a form of slow-acting network plasticity. To compare dentate granule cells (DGCs) generated during development with those born during adulthood, neural progenitor cells were labeled at either time point using retroviruses expressing different fluorescent proteins. Paired electrophysiological recordings were carried out in acute hippocampal slices to quantitatively study the major synaptic inputs onto mature DGCs: excitatory projections from the entorhinal cortex and inhibitory afferents from local interneurons. Our results show that DGCs generated in the developing and adult hippocampus converge into a remarkable similarity of network connectivity. These findings support a model in which the significance of adult neurogenesis relies on the continuous renewal of functional units with equivalent, rather than unique, physiological properties.