GABAergic interneurons play a crucial role in the generation of network activities. In the hippocampus, several types of synchronous network activities controlled by GAB Aergic interneurons have been described as the GiantDepolarizing Potentials (GDP) in immature animals or the slow, gamma and theta oscillations observed in the adult ones. These activities are associated with numerous physiological functions such as slow-wave sleep, memory and exploration processes. Network activity is determined by its structure and by the properties of synaptic transmission between the neurons that compose it. Our aim is to study the morpho-functional structure of the early GABAergic network, since, in the hippocampus; it is the first circuit to be functional. GABAergicsynapses are formed prior to glutamatergic ones. Dendritic projecting interneurons develop prior to peri-somatic projecting ones.
These data indicate that the early purely GABAergic network is strongly modified along astereotyped sequence, during the first post-natal week to be progressively interconnected with the excitatory network and to finally play a key role in the control of excitatory influx We will study slices from the immature hippocampus, using a double experimental strategy: an integrated approach using ultra-fast two-photon microscopy to image calcium transients with millisecond resolution to reconstruct the dynamics of the entire network activity with single-cell resolution, combined with a unitary approach using whole-cell multiple patch clamp recordings to characterize the physiological properties of the individual elements implicated in the network activity. This project will provide essential information to better understand the maturation of the GABAergic circuit that generate the main excitatory synaptic drive in the first post-natal week in the hippocampus.
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