Extrasynaptic δ-subunit containing GABA receptors.

γ-Aminobutyric acid type A receptors (GABARs) are GABA gated heteropentameric chloride channels responsible for the adult brain's primary inhibition. In specific brain cells, such as in the hippocampus, one of the subtypes of GABARs, the δ subunit containing GABARs (δ-GABARs), is predominantly expressed and located in extrasynaptic or perisynaptic positions. δ-GABARs mediate a slow constant inhibitory current called tonic inhibition. While δ-GABARs and tonic inhibition is critical for the excitability of single neurons, accumulating data suggest that the function of δ-GABARs are broader and includes an integrative role in the network oscillations. While these open new horizons on the neurobiology of δ-GABARs, the complexity continues to challenge the analysis of GABARs and their subtypes. This review will summarize the current knowledge of molecular, cellular and physiological characteristics of δ-GABARs during health and disease.