A low dose of the γ‐secretase inhibitor DAPT improves learning and memory by regulating the Na V 1.6/Notch axis in C57BL/6 male mice

Abstract Background and Purpose Cognitive impairment poses a major challenge in neurodegenerative diseases and inflammatory brain disorders due to limited treatment options. The voltage‐gated sodium channel Na V 1.6 is associated with synaptic plasticity and cognitive decline in APP/PS1 mice. DAPT, a γ‐secretase inhibitor that blocks Notch signalling, has variable cognitive effects depending on dosage. This study investigates the dose‐dependent effects of DAPT on cognition in C57BL/6 male mice, elucidating its mechanisms through Na V 1.6 channels, Notch signalling, synaptic plasticity, and neurogenesis. Experimental Approach Mice received unilateral stereotactic injections in the right hemisphere of low‐dose DAPT (1 μg·μl −1 ), high‐dose DAPT (2 μg·μl −1 ), or DMSO (control). Cognitive abilities were evaluated using the Morris Water Maze and Y‐maze, western blots, immunofluorescence, and RT‐qPCR analysed Na V 1.6, synaptic proteins, NMDA/AMPA receptors, and neuroinflammatory markers. Neurogenesis was assessed via Nissl and doublecortin (DCX) staining. Primary neuron experiments examined DAPT effects on Na V 1.6 interactions. Key Results Low‐dose DAPT significantly improved cognition, suppressed Notch pathway genes, reduced Na V 1.6, and up‐regulated synaptic proteins, NMDA/AMPA receptors, and neuronal markers in vivo/in vitro. In primary culture neurons, DAPT reduced Notch‐1/NICD with TTX but not ATX‐II. Inflammatory markers/cytokines were unchanged. In vitro, 5‐μM DAPT decreased Na V 1.6, increased Notch receptors and reduced Notch‐1/HES‐1 mRNA. Low‐dose DAPT enhanced neurogenesis (increased dentate gyrus DCX + cells). Molecular docking confirmed favourable DAPT‐ Na V 1.6 interactions. Conclusion and Implications Low‐dose DAPT improved cognitive function in C57BL/6 male mice, by modulating the Na V 1.6/Notch axis and enhancing neurogenesis, indicating its potential as a therapeutic strategy for Alzheimer's‐related cognitive decline.