title: Homeostatic control of the excitation-inhibition balance in cortical layer 5 pyramidal neurons.
abstract: Homeostatic regulation in the brain is thought to be achieved through a control of the synaptic strength by close interactions between excitation and inhibition in cortical circuits. We recorded in a layer 5 pyramidal neuron of rat cortex the composite response to an electrical stimulation of various layers (2-3, 4 or 6). Decomposition of the global conductance change in its excitatory and inhibitory components permits a direct measurement of excitation-inhibition (E-I) balance. Whatever the stimulated layer was, afferent inputs led to a conductance change consisting of 20% excitation and 80% inhibition. Changing synaptic strengths in cortical networks by using a high-frequency of stimulation (HFS) protocol or a low-frequency of stimulation (LFS) protocol (classically used to induce long-term potentiation or long-term depression at the synaptic level) were checked in order to disrupt this balance. Application of HFS protocols in layers 2-3, 4 or 6, or of LFS protocols in layer 4 induced, respectively, long-term paralleled increases or long-term paralleled decreases in E and I which did not change the E-I balance. LFS protocols in layers 2-3 or 6 decreased E but not I and disrupted the balance. It is proposed that regulatory mechanisms might be mainly sustained by recurrent connectivity between excitatory and inhibitory neuronal circuits and by modulation of shunting GABA(A) inhibition in the layer 5 pyramidal neuron.
authors.affiliation: CNRS, Institut de Neurobiologie Alfred Fessard, FRC2118, Laboratoire de Neurobiologie Cellulaire et Moléculaire, UPR9040, Gif sur Yvette, F-91198, France.
authors.forename: Nicolas
authors.initials: N
authors.lastname: Le Roux
authors.forename: Muriel
authors.initials: M
authors.lastname: Amar
authors.forename: Gérard
authors.initials: G
authors.lastname: Baux
authors.forename: Philippe
authors.initials: P
authors.lastname: Fossier
mesh_terms: D000818:Animals; D004307:Dose-Response Relationship, Radiation; D004553:Electric Conductivity; D004558:Electric Stimulation / Q000379:methods; D006706:Homeostasis / Q000502:physiology* / Q000528:radiation effects; D066298:In Vitro Techniques; D008564:Membrane Potentials / Q000502:physiology / Q000528:radiation effects; D009415:Nerve Net / Q000502:physiology / Q000528:radiation effects; D009433:Neural Inhibition / Q000187:drug effects / Q000502:physiology*; D009473:Neuronal Plasticity / Q000502:physiology / Q000528:radiation effects; D018408:Patch-Clamp Techniques / Q000379:methods; D017966:Pyramidal Cells / Q000502:physiology* / Q000528:radiation effects; D051381:Rats; D017208:Rats, Wistar; D018709:Statistics, Nonparametric; D013997:Time Factors; D014793:Visual Cortex / Q000166:cytology*