title: Tonic excitation or inhibition is set by GABA(A) conductance in hippocampal interneurons.
abstract: Inhibition is a physiological process that decreases the probability of a neuron generating an action potential. The two main mechanisms that have been proposed for inhibition are hyperpolarization and shunting. Shunting results from increased membrane conductance, and it reduces the neuron-firing probability. Here we show that ambient GABA, the main inhibitory neurotransmitter in the brain, can excite adult hippocampal interneurons. In these cells, the GABA(A) current reversal potential is depolarizing, making baseline tonic GABA(A) conductance excitatory. Increasing the tonic conductance enhances shunting-mediated inhibition, which eventually overpowers the excitation. Such a biphasic change in interneuron firing leads to corresponding changes in the GABA(A)-mediated synaptic signalling. The described phenomenon suggests that the excitatory or inhibitory actions of the current are set not only by the reversal potential, but also by the conductance.
authors: RIKEN Brain Science Institute (BSI), Wako, Saitama 351-0198, Japan.
authors: Inseon
authors: I
authors: Song
authors: Leonid
authors: L
authors: Savtchenko
authors: Alexey
authors: A
authors: Semyanov
mesh_terms: D000818:Animals; D003198:Computer Simulation; D004594:Electrophysiology; D005968:Glutamate Decarboxylase / Q000235:genetics; D006624:Hippocampus / Q000166:cytology*; D007395:Interneurons / Q000378:metabolism*; D051379:Mice; D018345:Mice, Knockout; D008954:Models, Biological; D009433:Neural Inhibition / Q000502:physiology*; D018408:Patch-Clamp Techniques; D005680:gamma-Aminobutyric Acid / Q000378:metabolism*
chemical_list: D005680:gamma-Aminobutyric Acid; D005968:Glutamate Decarboxylase; C401141:glutamate decarboxylase 2