Listening to Ketamine

Listening to Ketamine

Emily Underwood

The fast-acting drug offers a new way to treat depression and fathom its origins. Recent approval of a nasal spray promises to expand access, but much remains unknown about long-term use and the potential for abuse.

Bennett has now been receiving regular ketamine injections for 17 years, with few negative side effects, she says. She doesn’t consider herself addicted to ketamine because she feels no desire to take it between scheduled appointments. But she does feel dependent on the drug, in the same way that a person with high blood pressure takes medication for hypertension, she says.

Still, she acknowledges what most clinicians and researchers contend: There simply aren't enough data to know what the optimal dose for depression is, who is most likely to benefit from ketamine treatment and what long-term treatment should look like. “There’s a lot that we don’t know about how to use this tool,” Bennett says. “What’s the best dose? What’s the best route of administration? How frequently do you give ketamine treatment? What does maintenance look like? Is it OK to use this in an ongoing way?”

How Ketamine Changes the Depressed Patient's Brain

Simon Makin

Despite this excitement, researchers still don't know exactly how ketamine exerts its effects. A leading theory proposes that it stimulates regrowth of synapses (connections between neurons), effectively rewiring the brain. Researchers have seen these effects in animals' brains, but the exact details and timing are elusive.

A new study, from a team led by neuroscientist and psychiatrist Conor Liston at Weill Cornell Medicine, has confirmed that synapse growth is involved, but not in the way many researchers were expecting. Using cutting-edge technology to visualize and manipulate the brains of stressed mice, the study reveals how ketamine first induces changes in brain circuit function, improving "depressed" mice's behavior within three hours, and only later stimulating regrowth of synapses.

As well as shedding new light on the biology underlying depression, the work suggests new avenues for exploring how to sustain antidepressant effects over the long term. "It's a remarkable engineering feat, where they were able to visualize changes in neural circuits over time, corresponding with behavioral effects of ketamine," says Carlos Zarate, chief of the Experimental Therapeutics and Pathophysiology Branch at the National Institute of Mental Health, who was not involved in the study. "This work will likely set a path for what treatments should be doing before we move them into the clinic."