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Internships 2011

Tuning of EPSP-Spike Coupling and Timing by GABAergic Activity

Team : Plasticity of Neuronal Excitability and Epilepsy

Project advisor : Olivier Caillard, Research Scientist (CNRS)

Contact :

Summary :

Excitatory post synaptic potentials (EPSPs) underlie the principal mode of communication between neurons. The amplitude and shape of an EPSP determines both the probability and the precision at which the postsynaptic cell fires an action potential. Among the different parameters that control the voltage trajectory when a cell receive an excitatory input, inhibitory GABAergic activity plays an important role in controlling EPSP-spike coupling. Nevertheless, a general view on the influence of the different modes of inhibition, i.e. background, phasic and tonic activities on EPSP-spike coupling and timing is still missing.

I propose to examine the impact of different modes of GABAA activity using both experimental and modelling experiments in order to test how GABAA activity can affect spike probability and timing when a cell receives an EPSP as input. Since the reversal potential for GABAA PSP is a parameter that can vary according to development, activity and neurological diseases, different experiments will be performed in order to analyze the EPSP-spike coupling relationships in the presence of background, phasic and tonic modes of GABAA activity for different GABAA reversal potentials.

Simultaneous Recording of Membrane Potential and Intracellular Calcium in Cortical Neurons :
A. Whole Cell Recording of a Layer II/III pyramidal neuron. B. Action Potential discharge of the Neuron in response to a constant depolarising current. Note the variability of action potential timing. C. Whole Cell Recording of a Layer V pyramidal neuron. The cell was filled with a fluorescent calcium indicator (oregon green) that allows calcium measurements in the different cell compartments (dendrite, soma, axon see Regions of Interest in C). D. When the neurone is depolarised by DC current injection, the cell fires action potentials (AP) (5 AP@ 50 Hz here). A transient intracellular calcium increase can be observed in the soma but also proximal and distal dendrite. E. Same cell as in D but the neurone fires AP at a lower frequency (5 AP @ 6.7 Hz). See the gradual intracellular calcium increase during spike discharge.

Techniques and methods : in vitro Electrophysiology (Whole-Cell and Perforated Patch clamp Recordings), Dynamic Clamp, Calcium Imaging, Computer Modelling

INSERM UMR 641 - Laboratoire de Neurobiologie des Canaux Ioniques

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