Temporal Mapping of Adult-Born Granule Cells Integration in Two Major Local Inhibitory Populations of the Hippocampus

AYELEN I GROISMAN; ALEJANDRO F SCHINDER; SUNG M YANG

Cordoba Capital

Congreso; XXXIII Congress of the Argentine Society for Research in Neuroscience; 2018

Sociedad Argentina de Neurociencias

Adult neurogenesis provides a continuous pool of new granulecells (GCs) that participate in information processing inthe dentate gyrus of the hippocampus.We studied how GCsbecome integrated toward maturation into the preexistingcircuit of the adult mouse dentate gyrus. We chose twomajor populations of GABAergic interneurons (INs) of thehippocampus: parvalbumin expressing cells (PV) andsomatostatin expressing cells (SST). We combined optogeneticsand acute slice electrophysiology to activate PV orSST and GCs, retrovirally labeled, at different stages of maturationand studied their connectivity in both directions,interneuron to GCs, and vice versa. We built a temporalmap of synaptogenesis for each IN population and observedthat connectivity between PV and GCs (input and output)reached maturation when GCs were >6 weeks old. For SST,the inhibitory postsynaptic current increased gradually withGCs development, while the GC output connectivity developedmuch later (>11 weeks) compared to PV. We foundthat PV synapses onto GCs were located perisomatically andcontributed to both feedforward and feedback inhibitoryloops within the granule cell layer. In contrast, SST contactedGCs in proximal and distal dendrites and contributed only tofeedback inhibition. These data demonstrates that integrationof new GCs within the preexistent dentate GABAergicnetwork is specific of each IN population and that adultneurogenesis promotes a long-term plasticity for circuitremodeling.