Homomeric gamma-aminobutyric acid type A receptor (GABA_A receptor (homomeric))

The homomeric gamma-aminobutyric acid type A receptor, historically known as the GABA-C receptor, is a specialized ligand-gated ion channel composed of five identical rho (ρ) subunits (Enz & Cutting, 1998). These receptors are primarily expressed in the retina, where they play a pivotal role in visual signal processing by mediating slow and sustained inhibitory postsynaptic currents (IUPHAR/BPS Guide to PHARMACOLOGY). Unlike the more common heteromeric GABA_A receptors, homomeric rho receptors are characterized by their relative insensitivity to classic modulators such as benzodiazepines and barbiturates (Olsen & Sieghart, 2008). Upon binding the neurotransmitter GABA, the receptor undergoes a conformational change that opens a chloride-selective pore, leading to hyperpolarization of the neuron and inhibition of electrical activity (PubMed, PMID: 21518254). Beyond the visual system, these receptors are found in the hippocampus and brainstem, suggesting involvement in cognitive functions and sleep regulation (StatPearls, GABA Receptor). Dysregulation of homomeric GABA_A receptors is associated with various pathologies, including visual impairments like myopia and neurological conditions such as epilepsy (NCBI, Gene ID: 2554). Pharmacological targeting of these receptors offers a unique therapeutic window for treating CNS disorders without the broad sedative side effects typically seen with general GABA_A agonists. Current research explores the use of specific antagonists like TPMPA and agonists like muscimol to modulate these channels for therapeutic benefit in sensory and psychiatric disorders.

Other names

GABA-rho receptorGABA-C receptorRho-homomeric GABA receptorGABRR1GABRR2GABRR3

The receptor acts as a ligand-gated chloride channel; GABA binding triggers the opening of the pore, allowing chloride ions to flow into the cell, which hyperpolarizes the membrane and inhibits neuronal firing.