In the brain, information is transmitted from one neuron to a second one at the level of a specialized structure, the synapse. During a long time, the transmission of information in the brain was only a neuronal story. Indeed, it was considered that the synapse was made of only two neuronal components: a presynaptic terminal that releases neurotransmitters and a postsynaptic element that receives and integrates information. However, since the last two decades, a third protagonist, the astrocyte, has entered this story. This third partner plays crucial role as regulator. To do that, the astrocyte detects the synaptic signal, encodes activity and in turn modulates the transfer of information by releasing active substances name gliotransmitters. By releasing distinct gliotransmitters like purines, D-serine, or glutamate, the astrocyte modulates several levels of synaptic communication in the brain. However, we do not still know if an individual astrocyte releases several gliotransmitters and thus modulates several forms of synaptic communication at the level of synapses it covered. To push further the boundaries understanding of the processing of information in the brain, first, I propose to establish if an individual astrocyte releases several gliotransmitters. Then, in a second time, using state-of-the-art cellular imaging techniques during electrophysiological experiments, I will determine if at the level of a single synapse the astrocyte releases these gliotransmitters and if their respective release depends on distinct calcium dependent mechanisms. This project will have strong consequences on our current vision of the tripartite synapse. Indeed, if several gliotransmitters are released at the level of a single synapse, the third element will modulate appropriately distinct form of synaptic communication. Nowadays, if we want to understand how information is transmitted in the brain we have to understand how the tripartite synapse works.
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