Brain region-specific action of ketamine as a rapid antidepressant.

Ketamine, a rapid antidepressant, works by blocking N-methyl-d-aspartate receptors (NMDARs) specifically in the lateral habenula (LHb) of the brain, not in the hippocampus. In depressive-like mice, this regional selectivity depends on local neural activity and the availability of extrasynaptic NMDARs. Activating the hippocampus or inactivating the LHb reversed this sensitivity. Removing NMDARs from the LHb prevented ketamine's antidepressant effects and blocked the drug-induced rise in serotonin and brain-derived neurotrophic factor in the hippocampus. Identifying this primary brain target should help design more precise antidepressant treatments.

Study at a glance

Abstract

Ketamine has been found to have rapid and potent antidepressant activity. However, despite the ubiquitous brain expression of its molecular target, the N-methyl-d-aspartate receptor (NMDAR), it was not clear whether there is a selective, primary site for ketamine's antidepressant action. We found that ketamine injection in depressive-like mice specifically blocks NMDARs in lateral habenular (LHb) neurons, but not in hippocampal pyramidal neurons. This regional specificity depended on the use-dependent nature of ketamine as a channel blocker, local neural activity, and the extrasynaptic reservoir pool size of NMDARs. Activating hippocampal or inactivating LHb neurons swapped their ketamine sensitivity. Conditional knockout of NMDARs in the LHb occluded ketamine's antidepressant effects and blocked the systemic ketamine-induced elevation of serotonin and brain-derived neurotrophic factor in the hippocampus. This distinction of the primary versus secondary brain target(s) of ketamine should help with the design of more precise and efficient antidepressant treatments.