Ketamine’s mechanisms of rapid antidepressant activity: Evidence from preclinical studies

Abstract

Enthusiasm over the growing series of reports describing ketamine’s rapid onset of robust antidepressant activity in clinical trials has ignited a large number of back-translational efforts attempting to employ rodent models to better characterize the antidepressant properties of the drug and to improve our understanding of its underlying mechanisms of antidepressant action. On balance, these preclinical studies have yielded fairly consistent findings demonstrating that ketamine has a broad range of behavioral effects consistent with antidepressant activity in a variety of rodent models. Many of these studies further suggest that ketamine’s effects are unique from other classic antidepressant drugs in producing more durable effects in some models and more rapidly reversing the behavioral effects of chronic stressor exposure in other models. The preclinical studies are also beginning to elucidate the drug’s mechanisms of antidepressant activity, with the majority of recent studies suggesting that increased levels of regional alpha-amino-3-hydroxy-5-methyl-4-isoxazole proprionic acid (AMPA) receptor activation and brain-derived neurotrophic factor (BDNF) expression, as well as enhanced synaptic plasticity, are critical components of the response. However, there remain several points of disagreement and inconsistency in the preclinical literature that require additional investigation, including the effectiveness of other NMDA receptor-targeting drugs and the specific targets of ketamine’s proximal effects. This chapter provides an overview and critical review of this preclinical literature. It is anticipated that a more complete understanding of ketamine’s mechanisms of antidepressant action will allow for a safer and more efficient use of ketamine in the clinical setting and afford us new opportunities for novel drug development.