gamma-Aminobutyric acid type A (GABAA) receptor subtypes inverse agonists as therapeutic agents in cognition

The gabaergic system has been identified as a relevant regulator of cognitive and emotional processing. In fact, the discovery that negative allosteric regulators (or inverse agonists) at GABAA (g-aminobutyric acid) a5 subtype receptors improve learning and memory tasks, has further validated this concept. The localization of these extrasynaptic subtype receptors, mainly in the hippocampus, has suggested that they play a key role in the three stages of memory: acquisition, consolidation, and retrieval. The “a5 inverse agonist” binds to an allosteric site at GABAA receptor, provoking a reduction of chlorine current, but to elicit this effect, the necessary condition is the binding of agonist neurotransmitter (gamma-amino butyric acid) at its orthosteric site. In this case, the GABAA receptor is not a “constitutively active receptor” and, however, the presence of spontaneous opening channels for native GABAA receptors is rare. Here, we present various classes of nonselective and a5 selective GABAA receptor ligands, and the in vitro and in vivo tests to elucidate their affinity and activity. The study of the GABAA a5 inverse agonists is one of the important tools, although not the only one, for the development of clinical strategies for treatment of Alzheimer disease and mild cognitive impairment.