Convergence of distinct signaling pathways on synaptic scaling to trigger rapid antidepressant action

Ketamine is a noncompetitive glutamatergic N-methyl-D-aspartate receptor (NMDAR) antagonist that exerts rapid antidepressant effects. Preclinical studies identify eukaryotic elongation factor 2 kinase (eEF2K) signaling as essential for the rapid antidepressant action of ketamine. Here, we combine genetic, electrophysiological, and pharmacological strategies to investigate the role of eEF2K in synaptic function and find that acute, but not chronic, inhibition of eEF2K activity induces rapid synaptic scaling in the hippocampus. Retinoic acid (RA) signaling also elicits a similar form of rapid synaptic scaling in the hippocampus, which we observe is independent of eEF2K functioni. The RA signaling pathway is not required for ketamine-mediated antidepressant action; however, direct activation of the retinoic acid receptor alpha (RAR alpha) evokes rapid antidepressant action resembling ketamine. Our findings show that ketamine and RAR alpha activation independently elicit a similar form of multiplicative synaptic scaling that is causal for rapid antidepressant action.

Automated summary

Acute inhibition of eEF2K activity induces rapid synaptic scaling in the hippocampus, while RA signaling pathway can also elicit similar synaptic scaling independently of eEF2K function. Activation of RAR alpha by retinoic acid leads to rapid antidepressant effects similar to ketamine.