Acute d-serine treatment produces antidepressant-like effects in rodents

Summary

D-serine, a co-agonist at NMDA receptors, produces antidepressant-like effects in rodents. A single acute dose of D-serine reduced immobility in the forced swim test without affecting motor function, reversed sexual reward-seeking deficits caused by serotonin depletion, and reversed learned helplessness behavior. Mice lacking NMDA receptor NR1 subunits in forebrain excitatory neurons showed a depression-like phenotype and did not respond to D-serine. These findings suggest D-serine has antidepressant-like effects and support the idea of complex glutamatergic dysfunction in depression, though it remains unclear whether D-serine shares a convergent mechanism with NMDA antagonists like ketamine.

Study at a glance

Abstract

Research suggests that dysfunctional glutamatergic signalling may contribute to depression, a debilitating mood disorder affecting millions of individuals worldwide. Ketamine, a N-methyl-D-aspartate (NMDA) receptor antagonist, exerts rapid antidepressant effects in approximately 70% of patients. Glutamate evokes the release of D-serine from astrocytes and neurons, which then acts as a co-agonist and binds at the glycine site on the NR1 subunit of NMDA receptors. Several studies have implicated glial deficits as one of the underlying facets of the neurobiology of depression. The present study tested the hypothesis that D-serine modulates behaviours related to depression. The behavioural effects of a single, acute D-serine administration were examined in several rodent tests of antidepressant-like effects, including the forced swim test (FST), the female urine sniffing test (FUST) following serotonin depletion, and the learned helplessness (LH) paradigm. D-serine significantly reduced immobility in the FST without affecting general motor function. Both D-serine and ketamine significantly rescued sexual reward-seeking deficits caused by serotonin depletion in the FUST. Finally, D-serine reversed LH behaviour, as measured by escape latency, number of escapes, and percentage of mice developing LH. Mice lacking NR1 expression in forebrain excitatory neurons exhibited a depression-like phenotype in the same behavioural tests, and did not respond to D-serine treatment. These findings suggest that D-serine produces antidepressant-like effects and support the notion of complex glutamatergic dysfunction in depression. It is unclear whether D-serine has a convergent influence on downstream synaptic plasticity cascades that may yield a similar therapeutic profile to NMDA antagonists like ketamine.