Implications for Anesthesia and beyond

Abstract

Gamma-aminobutyric acid (GABA), a nonpeptide amino acid transmitter, is a major component of modern neuropharmacology and one of the most crucial target sites for general anesthetics and therapeutic drugs. GABA type A receptors (GABA ARs) are the most abundant inhibitory neurotransmitter receptors in the central nervous system. They are part of the rapid-acting, ligand-gated ion channel (LGIC) receptor category, a pentameric Cys-loop superfamily member that mediates inhibitory neurotransmission in the mature brain. GABA ARs mainly consist of two α subunits, two β subunits, and one additional subunit from either γ or δ arranged around a central chloride (Cl -) selective channel. Multiple GABA AR subunit subtypes and splice variants have been identified. Each variant of GABA AR exhibits distinct biophysical and pharmacologic properties. Several compounds allosterically modulate the GABA AR positively or negatively. The widely used positive GABA AR modulators include benzodiazepines (anxiolytic and anticonvulsant), general anesthetics (volatile agents like isoflurane, and intravenous agents like barbiturates, etomidate, and propofol), long-chain alcohols, some anticonvulsants, and neuroactive steroids. The binding sites for each drug are distinctly different. The anesthetic drugs enhance receptor-mediated synaptic transmission and thus interrupt the thalamocortical transmission, which controls the sleep-wake patterns. Abnormality in the GABA AR function has been implicated in several neurological conditions, such as sleep disorders, seizures, depression, cognitive function, neurological recovery after injury, and neuroplasticity. Understanding the GABA AR lays the foundation for the development of highly specific drugs in the treatment of neurological disorders and general anesthesia.