Scientists in the US have found how a commonly used anaesthetic is able to lift the symptoms of depression in hours, rather than weeks.
Their work reveals how the anaesthetic lifts depression, and it seems to act on neurons in an unusual way.
The team, led by Associate Professor Lisa Monteggia at the University of Texas Southwestern Medical Centre, have been examining the effects of the anaesthetic ketamine and similar compounds on depressed mice.
The group assessed how depressed the mice were by placing them in a beaker of water to undergo a "forced swim test". Depressed mice rapidly give up trying to swim.
Several small-scale studies of ketamine in patients with depression have shown that a single very low dose lifts depression within two hours and that the effect lasts for up to two weeks. Current medications for depression can take several weeks to work.
Monteggia's group found the same effect in their depressed mice, with one compound taking only 30 minutes to act. With ketamine, the antidepressant effect was still there a week later.
Monteggia is excited about the study's discovery of the mechanism behind ketamine's action.
What is surprising is that the ketamine seems to be working on neurons that are resting rather than actively firing. It seems to be making resting neurons even more relaxed.
"This is the first study to show that tonic resting nerve transmission is important in behaviour," ABC Science quoted Monteggia as saying.
"Drugs like this could have utility when say, an attempted suicide patient presents at the emergency room," Monteggia said.
The study has been published in this week's edition of Nature.