In vitro gamma oscillations following partial and complete ablation of δ subunit-containing GABA A receptors from parvalbumin interneurons

Perisynaptic and extrasynaptic δ subunit-containing GABA A receptors (δ-GABA A Rs) mediate tonic conductances in many neurons. On principal cells of the neocortex and hippocampus they comprise α4 subunits, whereas they usually contain α1 on various interneurons. Specific characteristics of δ-GABA A Rs are their pharmacology and high plasticity. In particular δ-GABA A Rs are sensitive to low concentrations of neurosteroids (NS) and during times of altered NS production (stress, puberty, ovarian cycle and pregnancy) δ-GABA A Rs expression varies in many neurons regardless of the α subunits they contain, with direct consequences for neuronal excitability and network synchrony. For example δ-GABA A Rs plasticity on INs underlies modifications in hippocampal γ oscillations during pregnancy or over the ovarian cycle.