Homeostatic control of the excitation-inhibition balance in cortical layer 5 pyramidal neurons.

Nicolas Le Roux (1, 2) , Muriel Amar (1, 2) , Gérard Baux (1, 2) , Philippe Fossier (1, 2)

1 INAF - Institut de Neurobiologie Alfred Fessard
2 NBCM - Laboratoire de neurobiologie cellulaire et moléculaire

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.

Domaines: Neurosciences [q-bio.NC]

Nicolas Le Roux, Muriel Amar, Gérard Baux, Philippe Fossier. Homeostatic control of the excitation-inhibition balance in cortical layer 5 pyramidal neurons.. European Journal of Neuroscience, 2006, 24 (12), pp.3507-18. ⟨10.1111/j.1460-9568.2006.05203.x⟩. ⟨hal-00147438⟩