Combinatorial targeting of NMDARs and 5-HT4Rs exerts beneficial effects in a mouse model of Alzheimer's disease.

BACKGROUND

Alzheimer's disease (AD) is the leading cause of dementia. There are limited approved medications that delay cognitive decline or lessen neuropsychiatric symptoms. Numerous clinical trials for AD using a single drug administration have failed to meet therapeutic endpoints, which is most likely due to the complexity of AD. A multimodal therapeutic intervention is more likely to improve symptoms by targeting multiple targets implicated in AD. Here, we investigated if targeting both N-Methyl-D-aspartic acid receptors (NMDARs) and serotonin type 4 receptors (5-HT4R) may have beneficial effects in a mouse model of AD, as they have separately been shown to improve cognition and/or mood.

METHODS

Male and female control (Ctrl) or APP/PS1 mice were administered single, intermittent, or chronic administration of 1) saline; 2) (R,S)-ketamine, an NMDAR antagonist; 3) prucalopride, a 5-HT4R agonist; or 4) (R,S)-ketamine + prucalopride to simultaneously target co-morbid neuropsychiatric and cognitive deficits. Behavioral assays were then administered to measure cognition, perseverative behavior, hyponeophagia, and/or sleep. Brains were processed for glial fibrillary acidic protein (GFAP) immunohistochemistry.

RESULTS

Single and chronic administration of (R,S)-ketamine + prucalopride administration improved cognitive decline by increasing memory retrieval in a contextual fear conditioning (CFC) paradigm in APP/PS1 mice. Drug efficacy was less effective in females than in males and was age dependent. Hippocampal GFAP immunoreactivity was decreased by chronic (R,S)-ketamine + prucalopride treatment in females.

CONCLUSIONS

Our results indicate that combined administration of (R,S)-ketamine + prucalopride is a novel multimodal therapeutic strategy to treat cognitive decline in AD. Future work will further characterize these interactions with the goal of clinical development.