Neurotrophic mechanisms underlying the rapid and sustained antidepressant actions of ketamine.

Summary

Depression is linked to reduced levels of neurotrophic factors like BDNF and VEGF, which contribute to neuronal atrophy in brain regions such as the prefrontal cortex and hippocampus, and to decreased adult neurogenesis. Conventional antidepressants partially reverse these deficits by inducing BDNF or VEGF but have limitations, including a delayed therapeutic response and low efficacy. Ketamine, an NMDA receptor antagonist, produces rapid (within hours) and sustained (up to a week) antidepressant effects in treatment-resistant depression and rodent models. In rodents, ketamine quickly increases BDNF and VEGF release in the medial prefrontal cortex and hippocampus, boosting spine synapses and hippocampal neurogenesis. These neurotrophic actions appear to underlie ketamine's rapid and sustained antidepressant effects, pointing toward development of faster-acting antidepressants with fewer side effects.

Study at a glance

Abstract

Clinical and preclinical studies have demonstrated that depression, one of the most common psychiatric illnesses, is associated with reduced levels of neurotrophic factors, including brain-derived neurotrophic factor (BDNF) and vascular endothelial growth factor (VEGF), contributing to neuronal atrophy in the prefrontal cortex (PFC) and hippocampus, and reduced hippocampal adult neurogenesis. Conventional monoaminergic antidepressants can block/reverse, at least partially, these deficits in part via induction of BDNF and/or VEGF, although these drugs have significant limitations, notably a time lag for therapeutic response and low response rates. Recent studies reveal that ketamine, an N-methyl-d-aspartate receptor antagonist produces rapid (within hours) and sustained (up to a week) antidepressant actions in both patients with treatment-resistant depression and rodent models of depression. Rodent studies also demonstrate that ketamine rapidly increases BDNF and VEGF release and/or expression in the medial PFC (mPFC) and hippocampus, leading to increase in the number and function of spine synapses in the mPFC and enhancement of hippocampal neurogenesis. These neurotrophic effects of ketamine are associated with the antidepressant effects of this drug. Together, these findings provide evidence for a neurotrophic mechanism underlying the rapid and sustained antidepressant actions of ketamine and pave the way for the development of rapid and more effective antidepressants with fewer side effects than ketamine.