The unpredictable grogginess experienced by patients waking up from general anesthesia may not be inevitable, suggests a recent mice study published in Proceedings of the National Academy of Sciences.

MIT researchers created specially-designed lab mice in order to test out a theory. The mice were bred to have nerve cells in the ventral tegmental area (VTA) of the brain that would only activate when a blue light was shined on them. This activation would in turn prompt the release of the neurotransmitter dopamine. The mice were first anesthetized, then the light was shone on the VTA neurons. As hoped for, the mice quickly woke up and some even began to walk around, seemingly restored to perfect health. While some evidence has shown that dopamine can wake us up from anesthesia, the study is one of the first to pinpoint how exactly it accomplishes this.

“The process of how the neural circuits come back online following anesthesia has not really been studied in depth,” said senior author Dr. Ken Solt in a MIT press release. “and this is something that interested us from a clinical standpoint, because we are investigating ways to rapidly reverse anesthesia.”

Solt, a research affiliate in the Department of Brain and Cognitive Sciences at MIT and an anesthesiologist at Massachusetts General Hospital, and his team have previously shown that ritalin can wake up anesthetized rats. It does so likely because it’s a stimulant that raises dopamine levels. Among its many functions, dopamine is already known to play a role in keeping us alert and awake. But the role of VTA dopamine neurons in doing so has been more elusive to determine.

“Dopamine neurons in the VTA are traditionally thought of as playing a key role in reward, motivation, and drug addiction but had not really been well characterized in the context of arousal,” Solt explained in the press release. “But we discovered that by activating dopamine neurons in this very specific part of the brain, we were able to reverse the state of general anesthesia and wake up the animals.”

Now armed with more evidence of dopamine’s usefulness, Solt’s team plans to expand their research. They will not only test the cognitive functions of mice woken up by dopamine, but also conduct clinical trials of Ritalin in human anesthesia patients. Should these trials pan out, they may very well signal a significant advance in post-surgery care.

“We want to get the patient’s cognitive processes back to exactly where they were before they had anesthesia,” said co-author Dr. Emery Brown, a fellow MIT researcher and anesthesiologist at Massachusetts General Hospital. “It’s a given that a high fraction of older patient’s brains in particular will not work as well after anesthesia.”

Elsewhere, some (but not all) research has shown that general anesthesia can increase the risk of developing delirium and other health complications. Shortening patients’ recovery time will undoubtedly help reduce that risk, the authors believe.

Source: Taylor N, Van Dort C, Kenny J, et al. Optogenetic Activation Of Dopamine Neurons In The Ventral Tegmental Area Induces Reanimation From General Anesthesia. Proceedings of the National Academy of Sciences. 2016.