Procognitive and neurotrophic benefits of α5-GABA-A receptor positive allosteric modulation in a β-amyloid deposition mouse model of Alzheimer's disease pathology.

Reduced somatostatin (SST) and SST-expressing GABAergic neurons are well-replicated findings in Alzheimer's disease (AD) and are associated with cognitive deficits. SST cells inhibit pyramidal cell dendrites through α5-GABA-A receptors (α5-GABAA-R). α5-GABAAR positive allosteric modulation (α5-PAM) has procognitive and neurotrophic effects in stress and aging models. We tested whether α5-PAM (GL-II-73) could prevent cognitive deficits and neuronal spine loss in early stages, and reverse them in late stages of β-amyloid deposition in the 5xFAD model (N = 48/study; 50 % female). Acute administration of GL-II-73 prevented spatial working memory deficits in 5xFAD mice at 2 months of age, while chronic administration reversed the deficits at 5 months of age. Chronic GL-II-73 treatment prevented 5xFAD-induced loss of spine density, spine count and dendritic length at both time points, despite β-amyloid accumulation. These results demonstrate procognitive and neurotrophic effects of GL-II-73 in early and late stages of Alzheimer-related β-amyloid deposition. This suggests α5-PAM as a novel β-amyloid-independent symptomatic therapeutic approach.