Control of contextual memory through interneuronal α5-GABAAreceptors

Abstract

Abstractγ-aminobutyric acid type A receptors that incorporate α5 subunits (α5-GABAARs) are highly enriched in the hippocampus and are strongly implicated in control of learning and memory. Receptors located on pyramidal neuron dendrites have long been considered responsible, but here we report that their selective knockout from either interneurons (α5-i-KO) or pyramidal neurons (α5-pyr-KO) interferes with the ability of the general anesthetic etomidate to suppress contextual conditioning. Using Ca2+imaging of CA1 pyramidal neuron activity in freely exploring mice to assess hippocampal function directly, we found that etomidate blocked the development of place cells and spatial engrams in wild type (WT) and α5-pyr-KO mice, but not in α5-i-KO mice. In addition, α5-i-KO mice developed weaker spatial engrams than WT mice under control conditions. These findings show that interneuronal α5-GABAARs serve a physiological role in promoting spatial learning, and that they mediate the suppression of hippocampus-dependent memory by etomidate.