Input processing by adult-born dentate granule cells

M BELEN PARDI; LUCAS A. MONGIAT; ALEJANDRO F. SCHINDER; ANTONIA MARÍN-BURGIN

Huerta Grande, Cordoba

Congreso; Reunión Anual Sociedad Argentina de Investigación en Neurociencias; 2012

Sociedad Argentina de Investigación en Neurociencias

The adult dentate gyrus (DG) generates new granule cells (GCs) that develop over several weeks and integrate into the preexisting network. Here, we examined whether immature adult-born GCs contribute to information encoding. We worked on acute hippocampal slices obtained from adult mice injected with a retrovirus to express RFP in newborn GCs. Using electrophysiological recordings of postsynaptic responses evoked by activation of the perforant path (PP), we observed that immature GCs required weaker stimuli than mature GCs to be activated, both after single pulses and after 10 Hz trains of stimuli. This suggest that while mature GCs are presumably more selective in their responses, immature GCs could be recruited by different inputs, allowing integrations to occur. To test this hypothesis, we monitored GC activity by loading them with the calcium-sensitive dye OGB-1 AM. Two electrodes were placed to stimulate different and independent PP inputs at various intensities. Under these conditions, the majority of mature GCs responded to only one of the two stimuli, but most immature GCs were recruited by both. Loose patch followed by whole cell recordings reveled that differences in activation profiles were a consequence of differences in the excitation/inhibition balance of afferent inputs. Immature GCs receive slower and weaker somatic inhibition than mature GCs. The observed functions could imply a differential role of mature and immature GCs in processing information arriving to the DG.