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Neurotransmitter action of glycine at inhibitory and excitatory synapses

Objective

To characterize with site-directed mutagenesis and patch-clamp three modulatory sites of the inhibitory glycine receptors (GlyRs) and of the glycine receptors associated with the NMDA receptors (NMDARs)
To characterize identified glycinergic synapses of the cerebellum and of the spinal cord by electrophysiology, immunochemistry and electron microscopy
To identify and characterize mutations of the glycine inhibitory receptors associated with motor disorders

The first aim of this project is to pursue the characterization of the two types of 'glycine receptors' known to exist in the vertebrate central nervous system: the strychnine-sensitive receptors (GlyRs), through which glycine acts as an inhibitory transmitter which opens Cl channels, and the NMDA receptor, on which glycine acts as an excitatory "coagonist" of L-glutamate. By taking advantage of the recent cloning of the various subunits of the two receptors, we will try to identify on both GlyRs and NMDARs the molecular determinants of some of the sites which either bind glycine or modulate its binding. Efforts will be focused on a new class of sites which potentiate the activation of GlyRs. We shall also identify and characterize new mutant GlyRs involved in human motor disorders such as hyperexplexia, and compare the effects of mutations affecting the alpha and the beta subunits of inhibitory glycine receptors.
From a more functional point of view, we will characterize the synaptic functions of glycine and attempt in particular to demonstrate that, at some synapses at least, a glycinergic terminal can trigger both the inhibitory and excitatory effects traditionally perceived as spatially and functionally separate. These experiments will be conducted both in the cerebellum and in spinal cord preparations where there is evidence that, at some synapses, the two types of glycine receptors are located in close proximity. We will examine if the phasic release of glycine by a glycinergic neurone can influence the NMDA receptors of a neighbouring glutamatergic synapse.
From the pharmacological point of view, we shall extend the search for compounds either potentiating the effects of glycine on GlyRs (such compounds are expected to inhibit motoneuronal activities and therefore to act as relaxants) or inhibiting the action of glycine on NMDARs (such compounds are expected to reduce the excitotoxic effects of excess glutamate and thus to act as neuroprotectants).

Funding Scheme

CSC - Cost-sharing contracts
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Coordinator

Centre National de la Recherche Scientifique
Address
46,Rue D'ulm
75230 Paris
France

Participants (4)

Ecole Normale Supérieure
France
Address
46,Rue D'ulm 46
75230 Paris
Karolinska Institute
Sweden
Address
12,Karolinska Institutet
171 77 Stockholm
Max-Planck-Gesellschaft zur Förderung der Wissenschaften e.V.
Germany
Address
46,Deutschordenstrasse
60496 Frankfurt
UNIVERSITY OF ERLANGEN-NUREMBERG
Germany
Address
Fahrstrasse 17
91054 Erlangen