Ketamine has equipotent effects on mechanisms other than NMDA receptor inhibition.

Current hypotheses for ketamine's antidepressant activity are critically reviewed.

Multiple aspects of serotonergic neurotransmission are modulated by ketamine.

Antidepressant-like effects seem to depend on endogenous 5-HT receptor activation.

Recent data predominantly support a role for 5-HT_1A or 5-HT_1B receptors.