One of the fundamental questions in neurobiology is how synapses are formed. Dendritic filopodia are thought to play an important role in the generation of excitatory synapses on dendritic spines.
They find and make initial contact with an appropriate axon and then retract to the dendrite and become spines. Much less is known about the role of filopodia - if any - in the generation of synapses on the dendritic shaft.
The aim of the proposed project is to elucidate this process by following the formation of shaft synapses using two-photon laser scanning microscopy. Most studies on synapse formation have concentrated on excitatory synapses, but I will examine inhibitory synapses, which never occur on spines.
Postsynaptic dendrites of pyramidal cells and GABAergic axons will be visualized with different fluorescent labels in hippocampal slice cultures by filling individual neurons and/or by using transgenic mice that express Green Fluorescent Protein (GFP) in a specific subset of neurons.
I will follow the morphological changes of the axon and dendrite at locations where they make contact. The formation of functional synapses will be verified by FM1-43 labelling, which marks presynaptic terminals that recycle vesicles. Once the initial events in GABAergic synapse formation under control conditions have been established, I will assess the regulation of these events by factors that are known to have an effect on GABAergic synapse formation.
Such factors could be pharmacological agents such as TTX, bicuculline and BDN F, or postsynaptic Cl- concentration. The results of the proposed experiments will lead to a better understanding of the initial steps in GABAergic synapse formation and factors influencing this process.
This will contribute to the understanding how neuron al networks are formed during development and how they can continue to remodel during learning and adaptation.
Fields of science
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