Improvement of Cognitive Functions And Neurotrophic Effects through by Α5‐GABAA Receptor Positive Allosteric Modulation in Animal Models of Risk for Alzheimer’s Disease

Abstract

AbstractBackgroundReduced GABA/somatostatin (SST) signaling is reported in psychiatric, stress‐related and neurodegenerative disorders. SST+ interneurons from cortical layers and the hippocampus inhibit the dendrites of excitatory neurons, largely through α5‐containing GABAA receptors (α5‐GABAAR). Recently, we showed that an α5‐positive allosteric modulator (α5‐PAM) alleviates working memory deficits and reverses neuronal atrophy in old mice. We then started to investigate the behavioral and neurotrophic effects of this α5‐PAM in animal models of aging, chronic stress, and β‐amyloid load, as risk factor for developing Alzheimer’s disease.MethodThree studies are presented, with ∼12 mice/group, 50% female: 1) Young C57BL6 subjected to unpredictable chronic mild stress (UCMS) to induce cognitive deficits. 2) 22 month‐old C57BL6 developing an age‐related cognitive decline. 3) 5xFAD transgenic mice with progressive amyloid‐related cognitive decline. In all studies, efficacy of chronic administration of GL‐II‐73 (30mg/kg, p.o, for 4 weeks) at rescuing cognitive deficits across 3 domains was assessed. Working memory was assessed in an alternation task, spatial memory in the water maze, and cognitive flexibility in a set‐shifting assay. Brains were then stained using Golgi‐Cox technique (n = 4brain/group; 8cell/brain) for quantification of dendritic length and spine density in the prefrontal cortex and hippocampus (NeuroLucida).ResultChronic treatment in all models reversed cognitive deficits across domains (ps<0.01), with a strong effect on working memory. Chronic treatment also significantly reversed UCMS‐, age‐, or amyloid‐induced dendritic shrinkage and reduction of spine density at apical and basal dendrites (p<0.001 in PFC and CA1).ConclusionTogether, results support that selective α5 targeting of GABAA receptors overcomes chronic stress‐, aging‐, or amyloid‐related cognitive deficits and detriments in neuronal morphology. This represents the first intervention targeting the GABAergic system to have a symptomatic and disease‐modifying therapeutic potential in a transdiagnostic manner. This could represent a major avenue for clinical development for patients suffering from cognitive deficits across brain disorders.