Integration of adult-born granule cells in local inhibitor y networks

GROISMAN AI; YANG SM; TEMPRANA SG; TRINCHERO MF; SCHINDER AF

Buenos Aires

Congreso; FALAN; 2016

Society for Research in Neuroscience

Adult neurogenesis provides a continuous pool ofnew granule cells (GCs) that participate in informationprocessing in the dentate gyrus of the hippocampus, whichis involved in memory and learning. As new GCs transitiontowards maturity, they reliably recruit GABAergic feedbackloops that restrict spiking of neighbor GCs, a mechanismthat would promote sparse coding. These are primarilymediated by interneurons (INs) expressing parvalbumin.We now investigated the role of somatostatin cells (SSTcs),one of the main populations of GABAergic INs in thehippocampus. SSTcs are thought to play a role in cognitionby modulating the GC response. We applied optogeneticsin transgenic mice and retroviral expression of transgenesto manipulate the activity of new GCs or SSTcs in order tomonitor synaptogenesis. As a first approach, we studiedoverall SST inhibition on the granule cell layer and foundthat activation of SSTcs may reduce the amplitude of thepopulation spike elicited by synchronous activation of theperforant path by 60%. We are currently investigating thedevelopment of synaptic connections in both directions, SSTto GCs and viceversa, at different stages of GCs maturation.Preliminary data indicates that SSTcs target the dendrites ofGCs already at immature stages, whereas GCs seem to reachSSTcs only upon maturation. These data are consistent withour previous findings that adult born GCs are uncoupledfrom inhibitory networks during early development.