The ketamine metabolite (2R,6R)-hydroxynorketamine rescues hippocampal mRNA translation, synaptic plasticity and memory in mouse models of Alzheimer's disease

Impaired synaptic plasticity and progressive memory deficits are major hallmarks of Alzheimers disease (AD). Hippocampal mRNA translation, required for memory consolidation, is defective in AD. Here, we show that systemic treatment with (2R,6R)- hydroxynorketamine (HNK), an active metabolite of the antidepressant ketamine, prevented deficits in hippocampal mRNA translation, long-term potentiation (LTP) and memory induced by AD-linked amyloid-{beta} oligomers (A{beta}Os) in mice. HNK activated hippocampal extracellular signal-regulated kinase 1/2 (ERK1/2), mechanistic target of rapamycin (mTOR), and p70S6 kinase 1 (S6K1)/ribosomal protein S6 (S6), which promote protein synthesis and synaptic plasticity. Stimulation of S6 phosphorylation by HNK was mTORC1-dependent, while rescue of hippocampal LTP and memory in HNK-treated A{beta}O-infused mice was ERK1/2-dependent and, partially, mTORC1- dependent. Remarkably, treatment with HNK corrected LTP and memory deficits in aged APP/PS1 mice. Transcriptomic analysis further showed that HNK rescued signaling pathways that are aberrant in APP/PS1 mice, including inflammatory and hormonal responses, and programmed cell death. Taken together, our findings demonstrate that HNK induces signaling and transcriptional responses that correct deficits in hippocampal synaptic plasticity and memory in AD mouse models. These results raise the prospect that HNK could serve as a therapeutic to prevent or reverse memory decline in AD.