Understanding how laughing gas can fight depression

Although a plethora of medications and therapies now exist for major depression, roughly one in three diagnosed patients still suffer from treatment-resistant depression (TRD) — a form of the disorder that does not respond to first-line antidepressants. Even when traditional drugs work, they often take weeks to kick in, delaying relief for people in crisis.

In response to this need, scientists have recently begun investigating whether fast-acting agents with different neurological effects could serve as alternative antidepressants. Encouraged by initial successes with ketamine, researchers including Peter Nagele, MD, Professor of Anesthesia and Psychiatry at the University of Chicago Medicine, turned to another anesthetic: nitrous oxide, better known as “laughing gas.”

Early clinical studies showed promise, so Nagele and his collaborators wanted to understand more about what exactly happens inside the brain during and after laughing gas treatment. In a new study published in Nature Communications, they pinpointed a novel neurological mechanism that helps explain how a gas that exits the body in minutes can trigger lasting improvements in mood.

“Figuring out how the observed antidepressant effects work at a neuronal and molecular level is an important step toward clinical acceptance and implementation,” said Nagele, the senior author of the new paper.

A new use for a familiar anesthetic

Most people associate laughing gas with dentists’ offices, where it’s used to ease anxiety and dull pain. While its nickname hints at euphoric effects, at the low doses used for depression research, it acts as a sedative, giving people a temporary feeling of calm, rather than making them feel giddy.

“Nitrous oxide is the oldest anesthetic we’ve got — it’s been used worldwide for over 180 years, costs about $20 a tank, and yet we’re still learning what it can do,” said first author Joseph Cichon, MD, PhD, an assistant professor of Anesthesiology and Critical Care at the University of Pennsylvania. “I felt like Indiana Jones, going back in time to crack the mystery of this ancient drug.”

In the preliminary clinical trials led by Nagele and researchers at Washington University in St. Louis, even a single inhalation session could bring positive change to patients who hadn’t responded to other treatments, with effects lasting up to two weeks in some cases.

“The results were striking,” Nagele said. “We saw people who had been struggling for years experience meaningful improvement within hours that lasted for weeks. It made us wonder what, exactly, was happening in the brain to cause this.”

Defying expectations about brain activity

For years, scientists assumed the antidepressant effects of both nitrous oxide and ketamine were tied to the drugs’ ability to block specific proteins on brain cells involved in memory and learning: N-methyl-D-aspartate (NMDA) receptors. But while this theory was widely accepted, it had never been fully tested in neuronal circuits of living brains. More importantly, it didn’t fully explain why nitrous oxide, which leaves the brain and body very quickly, could produce lasting effects.

To investigate, the researchers from UChicago, UPenn and WashU used advanced calcium imaging to observe brain activity in mice that inhaled nitrous oxide after being exposed to chronic stress — a common model for depression. Looking at the cingulate cortex, a brain region associated with emotional regulation and mood, they zeroed in on a specific group of neurons known as layer V (L5) pyramidal neurons.

“Particularly in stress-related depression, we usually see that these L5 neurons are underactive,” Nagele said.

In the experimental mice, however, the researchers saw that nitrous oxide quickly and selectively activated L5 neurons, pulling them out of their state of stress-induced inactivity even after the gas left mice’s bodies. The previously-stressed mice almost immediately perked up and started doing more enjoyable activities like sipping sugar water.

“This ‘disinhibition’ effect’ — where the brain becomes less suppressed and more engaged — looks to be a crucial reason for the drug’s antidepressant benefits,” Nagele explained. “It helps reactivate neural circuits dulled by stress and depression without needing to form entirely new brain connections.”

The key turned out to be specialized potassium channels found in L5 neurons, called SK2 channels. Under normal conditions, these channels help reduce neuron activity, but nitrous oxide blocks the SK2 channels. As a result, the neurons boost their activity and the surrounding brain circuit shifts into a more excitable, energized state.

Steps toward a new generation of depression treatments

“These results show us there might be more than one path to the desired outcome in depression treatment,” Nagele said. “NMDA receptors matter, but what we’re seeing with nitrous oxide suggests there’s another way to spark the brain’s circuitry back into action. It’s an exciting discovery because it widens our understanding of how we can tackle depression from multiple angles.

The researchers caution that while the findings are promising, more studies are needed to understand how long the neurological effects of laughing gas last and whether they contribute to deeper, more permanent recovery.

However, this fresh understanding of how fast-acting antidepressants might work — without relying solely on NMDA-receptor mechanisms — opens the door to future drug development. For example, rather than relying on an inhaled gas that must be clinically administered, scientists might one day design oral medications that mimic this mechanism.

“This study brings us one step closer to understanding how nitrous oxide can help patients who haven’t responded to anything else,” Nagele said. “If we can isolate the exact pathways involved, we could create new depression treatments that are more accessible and longer-lasting.”

“Nitrous oxide activates layer 5 prefrontal neurons via SK2 channel inhibition for antidepressant effect” was published in Nature Communications in April 2025. The research was funded by the National Institutes of Health (R35GM151160-01, K08GM139031, R01GM088156, R01GM151556, MH122379) and the Brain & Behavior Research Foundation. Co-authors include Joseph Cichon, Thomas Joseph, Xinguo Lu, Andrzej Wasilczuk, Max Kelz, Steven Mennerick, Charles Zorumski and Peter Nagele.