title: Presynaptic hyperpolarization induces a fast analogue modulation of spike-evoked transmission mediated by axonal sodium channels.
abstract: In the mammalian brain, synaptic transmission usually depends on presynaptic action potentials (APs) in an all-or-none (or digital) manner. Recent studies suggest, however, that subthreshold depolarization in the presynaptic cell facilitates spike-evoked transmission, thus creating an analogue modulation of a digital process (or analogue-digital (AD) modulation). At most synapses, this process is slow and not ideally suited for the fast dynamics of neural networks. We show here that transmission at CA3-CA3 and L5-L5 synapses can be enhanced by brief presynaptic hyperpolarization such as an inhibitory postsynaptic potential (IPSP). Using dual soma-axon patch recordings and live imaging, we find that this hyperpolarization-induced AD facilitation (h-ADF) is due to the recovery from inactivation of Nav channels controlling AP amplitude in the axon. Incorporated in a network model, h-ADF promotes both pyramidal cell synchrony and gamma oscillations. In conclusion, cortical excitatory synapses in local circuits display hyperpolarization-induced facilitation of spike-evoked synaptic transmission that promotes network synchrony.
authors.affiliation: INSERM, UMR_S 1072, Faculté de Médecine Secteur Nord, Boulevard Pierre Dramard, Marseille 13344, France.|UNIS, Faculté de Médecine Secteur Nord, Boulevard Pierre Dramard, Marseille 13344, France.|Aix-Marseille University, 13015 Marseille, France.
authors.forename: Sylvain
authors.initials: S
authors.lastname: Rama
authors.affiliation: INSERM, UMR_S 1072, Faculté de Médecine Secteur Nord, Boulevard Pierre Dramard, Marseille 13344, France.|UNIS, Faculté de Médecine Secteur Nord, Boulevard Pierre Dramard, Marseille 13344, France.|Aix-Marseille University, 13015 Marseille, France.
authors.forename: Mickaël
authors.initials: M
authors.lastname: Zbili
authors.affiliation: INSERM, UMR_S 1072, Faculté de Médecine Secteur Nord, Boulevard Pierre Dramard, Marseille 13344, France.|UNIS, Faculté de Médecine Secteur Nord, Boulevard Pierre Dramard, Marseille 13344, France.|Aix-Marseille University, 13015 Marseille, France.
authors.forename: Andrzej
authors.initials: A
authors.lastname: Bialowas
authors.affiliation: INSERM, UMR_S 1072, Faculté de Médecine Secteur Nord, Boulevard Pierre Dramard, Marseille 13344, France.|UNIS, Faculté de Médecine Secteur Nord, Boulevard Pierre Dramard, Marseille 13344, France.|Aix-Marseille University, 13015 Marseille, France.
authors.forename: Laure
authors.initials: L
authors.lastname: Fronzaroli-Molinieres
authors.affiliation: INSERM, UMR_S 1072, Faculté de Médecine Secteur Nord, Boulevard Pierre Dramard, Marseille 13344, France.|UNIS, Faculté de Médecine Secteur Nord, Boulevard Pierre Dramard, Marseille 13344, France.|Aix-Marseille University, 13015 Marseille, France.
authors.forename: Norbert
authors.initials: N
authors.lastname: Ankri
authors.affiliation: INSERM, UMR_S 1072, Faculté de Médecine Secteur Nord, Boulevard Pierre Dramard, Marseille 13344, France.|UNIS, Faculté de Médecine Secteur Nord, Boulevard Pierre Dramard, Marseille 13344, France.|Aix-Marseille University, 13015 Marseille, France.
authors.forename: Edmond
authors.initials: E
authors.lastname: Carlier
authors.affiliation: INSERM, UMR_S 1072, Faculté de Médecine Secteur Nord, Boulevard Pierre Dramard, Marseille 13344, France.|UNIS, Faculté de Médecine Secteur Nord, Boulevard Pierre Dramard, Marseille 13344, France.|Aix-Marseille University, 13015 Marseille, France.
authors.forename: Vincenzo
authors.initials: V
authors.lastname: Marra
authors.affiliation: INSERM, UMR_S 1072, Faculté de Médecine Secteur Nord, Boulevard Pierre Dramard, Marseille 13344, France.|UNIS, Faculté de Médecine Secteur Nord, Boulevard Pierre Dramard, Marseille 13344, France.|Aix-Marseille University, 13015 Marseille, France.
authors.forename: Dominique
authors.initials: D
authors.lastname: Debanne
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D001369:Axons / Q000502:physiology*; D001921:Brain / Q000166:cytology / Q000502:physiology; D002118:Calcium / Q000378:metabolism; D003198:Computer Simulation; D005260:Female; D008297:Male; D008564:Membrane Potentials / Q000502:physiology*; D008954:Models, Biological; D009415:Nerve Net / Q000502:physiology; D009474:Neurons; D017729:Presynaptic Terminals; D051381:Rats; D015222:Sodium Channels / Q000378:metabolism*
chemical_list: D015222:Sodium Channels; D002118:Calcium