Ambient GABA-activated tonic inhibition sharpens auditory coincidence detection via a depolarizing shunting mechanism.

Ambient GABA-activated tonic inhibition sharpens auditory coincidence detection via a depolarizing shunting mechanism.

Tang Zheng-Quan; Dinh Emilie Hoang; Shi Wei; Lu Yong

The Journal of neuroscience : the official journal of the Society for Neuroscience

2011

2011-04

Tonic inhibition mediated by extrasynaptic GABA(A) receptors (GABA(A)Rs) has emerged as a novel form of neural inhibition in the CNS. However, little is known about its presence and function in the auditory system. Using whole-cell recordings in brain slices, we identified a tonic current mediated by GABA(A)Rs containing the delta subunit in middle/high-characteristic-frequency neurons of the chicken nucleus laminaris, the first interaural time difference encoder that computes information for sound localization. This tonic conductance was activated by ambient concentrations of GABA released from synaptic vesicles. Furthermore, pharmacological manipulations of the conductance demonstrated its essential role in coincidence detection. Remarkably, this depolarizing tonic conductance was strongly inhibitory primarily because of its shunting effect. These results demonstrate a novel role for tonic inhibition in central auditory information processing.

Animals; Chick Embryo; Patch-Clamp Techniques; Electric Stimulation; Neurons/*physiology; gamma-Aminobutyric Acid/*physiology; Membrane Potentials/physiology; Auditory Pathways/*physiology; Neural Inhibition/*physiology; Inhibitory Postsynaptic Potentials; Receptors; Blotting; Western; GABA-A/*physiology

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