Abstract Anesthetics and anticonvulsants act, in part, through diverse populations of type-A ɣ-aminobutyric acid receptors (GABAARs) formed from a pool of 19 subunits. In the hippocampus, α5 subunits primarily coassemble with β3 and, in some cases, γ2, generating numerous subtypes with differential functional and pharmacological properties critical in learning and memory. The stoichiometry, structure, and gating of these subpopulations are poorly understood.