Influence of young vs. mature adult-born dentate granule cells on CA3 in vivo.

KROPFF, E.; PIATTI, VERÓNICA C.; MUGNAINI, M.; SCHINDER, A. F.

Mar del Plata

Congreso; XXXII Congreso Anual SAN; 2017

The hippocampal dentate gyrus is among the few areas of the adult mammalian brain that constantly incorporates new neurons. Ex vivo experiments revealed that young granule cells (GCs) are more excitable than mature GCs, while both populations evoke similar postsynaptic potentials on their main target neurons in CA3. However, the influence of young vs. mature GCs on CA3 in vivo remains unknown. Here we show CA3 neuronal activity recorded while mice explored different environments, with or without optogenetic stimulation of young and mature GCs of the same cohort (longitudinal analysis). Our preliminary data suggest that stimulation of mature GCs evokes greater local field potentials in CA3 than young GCs. Furthermore, only the mature population evokes greater responses at 1 Hz than 0.1 Hz, suggesting differential facilitation effects. Ongoing experiments explore this phenomenon at higher stimulating frequencies and varying intensities. On the other hand, we identified three frequency bands in the local field potential that coordinate their amplitude with theta oscillations. Preliminary analyses suggest that exposing mice to an enriched environment potentiates the coupling at high frequencies but reduces it at low frequencies. This effect is partially reverted upon stimulation of adult-born GCs. These results suggest that CA3 information processing is dissimilarly affected by adult born GCs at different maturational stages.