title: Depolarizing GABA/glycine synaptic events switch from excitation to inhibition during frequency increases.
abstract: By acting on their ionotropic chloride channel receptors, GABA and glycine represent the major inhibitory transmitters of the central nervous system. Nevertheless, in various brain structures, depolarizing GABAergic/glycinergic postsynaptic potentials (dGPSPs) lead to dual inhibitory (shunting) and excitatory components, the functional consequences of which remain poorly acknowledged. Indeed, the extent to which each component prevails during dGPSP is unclear. Understanding the mechanisms predicting the dGPSP outcome on neural network activity is therefore a major issue in neurobiology. By combining electrophysiological recordings of spinal embryonic mouse motoneurons and modelling study, we demonstrate that increasing the chloride conductance (g(Cl)) favors inhibition either during a single dGPSP or during trains in which g(Cl) summates. Finally, based on this summation mechanism, the excitatory effect of EPSPs is overcome by dGPSPs in a frequency-dependent manner. These results reveal an important mechanism by which dGPSPs protect against the overexcitation of neural excitatory circuits.
authors.affiliation: Univ. Bordeaux, INCIA, UMR 5287, F-33615 Pessac, France.|CNRS, INCIA, UMR 5287, F-33615 Pessac, France.
authors.forename: Pascal
authors.initials: P
authors.lastname: Branchereau
authors.affiliation: Univ. Bordeaux, INCIA, UMR 5287, F-33615 Pessac, France.|CNRS, INCIA, UMR 5287, F-33615 Pessac, France.
authors.forename: Daniel
authors.initials: D
authors.lastname: Cattaert
authors.affiliation: Univ. Bordeaux, INCIA, UMR 5287, F-33615 Pessac, France.|CNRS, INCIA, UMR 5287, F-33615 Pessac, France.
authors.forename: Alain
authors.initials: A
authors.lastname: Delpy
authors.affiliation: Univ. Bordeaux, INCIA, UMR 5287, F-33615 Pessac, France.|CNRS, INCIA, UMR 5287, F-33615 Pessac, France.
authors.forename: Anne-Emilie
authors.initials: AE
authors.lastname: Allain
authors.affiliation: Univ. Bordeaux, INCIA, UMR 5287, F-33615 Pessac, France.|CNRS, INCIA, UMR 5287, F-33615 Pessac, France.
authors.forename: Elodie
authors.initials: E
authors.lastname: Martin
authors.affiliation: Univ. Bordeaux, INCIA, UMR 5287, F-33615 Pessac, France.|CNRS, INCIA, UMR 5287, F-33615 Pessac, France.
authors.forename: Pierre
authors.initials: P
authors.lastname: Meyrand
mesh_terms: D000818:Animals; D002712:Chlorides / Q000737:chemistry; D004622:Embryo, Mammalian; D019706:Excitatory Postsynaptic Potentials / Q000187:drug effects*; D005998:Glycine / Q000494:pharmacology*; D007539:Isonicotinic Acids / Q000494:pharmacology; D051379:Mice; D008856:Microscopy, Fluorescence; D009046:Motor Neurons / Q000187:drug effects / Q000502:physiology; D018408:Patch-Clamp Techniques; D013116:Spinal Cord / Q000187:drug effects / Q000502:physiology; D005680:gamma-Aminobutyric Acid / Q000494:pharmacology*
chemical_list: D002712:Chlorides; D007539:Isonicotinic Acids; D005680:gamma-Aminobutyric Acid; D005998:Glycine; C015300:isoguvacine