[The next psychoactive drugs: From imipramine to ketamine]

Since the 1950s, the therapeutic arsenal against depression has grown considerably. From the discovery of monoamine oxidase inhibitors (MAOI) to the antidepressant effect of ketamine, these pharmacological breakthroughs made the history of psychiatry. They also guided the research about the pathophysiology of depression, one of the most devasting diseases, which affects between 10 and 20 % of general population. In this article, we offer a short historical review of the various therapeutic options developed over the past century and the consequences of these innovations. We then review the most recent one, ketamine (and its enantiomer S, esketamine). Ketamine's effects are spectacular both in terms of their very short onset time, and because they are observed even in treatment-resistant depression. Just as MAOIs and tricyclic antidepressants allowed the "monoaminergic hypothesis of depression" to emerge, to unravel the mechanisms of ketamine's antidepressant effects should allow the understanding of the role of glutamatergic system, or that of neuro-inflammation, in the neurobiology of depression. Ketamine might also help to refine our understanding of the cognitive pathophysiology of depression, or even to deeply transform the clinical representations about what depression is.