Gamma-aminobutyric acid type A receptor alpha4-delta subunit (GABA_A receptor alpha4-delta subunit)

The gamma-aminobutyric acid type A receptor alpha4-delta subunit refers to a specific subtype of the heteropentameric GABA_A ionotropic chloride channel composed primarily of two alpha-four (alpha4), two beta (beta2/beta3), and one delta (delta) subunits. These extrasynaptic receptors mediate tonic rather than phasic inhibition—providing persistent background suppression of neuronal activity distinct from synaptically localized benzodiazepine-sensitive forms containing gamma-subunits. The presence of both alpha4 and delta confers unique pharmacological properties including insensitivity to benzodiazepines but high sensitivity to neurosteroids like allopregnanolone as well as ethanol. They are highly expressed in brain regions such as thalamus, hippocampus dentate gyrus granule cells, neocortex pyramidal cells, cerebellar granule cells—where they play critical roles in regulating network excitability during development and adulthood. Dysfunction or altered expression is implicated in epilepsy susceptibility, anxiety states, sleep regulation abnormalities and possibly alcohol use disorder due to their ethanol sensitivity.[1][2][3][5][6][7]

Other names

GABA_A receptor alpha4-delta subunitGABRD (for the delta subunit gene)[4]Gamma-aminobutyric acid type A receptor delta subunit[4]delta-GABA_A receptor[4][5]Alpha4-beta2-delta GABA-A receptor (alpha4beta2delta)[5]

Positive allosteric modulation by neurosteroids enhances tonic inhibition mediated by alpha4betadelta-containing GABA_A receptors[7]. Direct agonism by gaboxadol or similar compounds increases chloride influx, hyperpolarizing neurons and reducing excitability[5]. Ethanol potentiation increases tonic inhibitory currents through these channels at physiologically relevant concentrations[7].