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Goodbye Pills: Light Could Be the Painkiller of the Future

Scientists activated opiate receptors in mice with light.
Image: Flickr/Richard Leeming

It's 2025, and you just had had a brain operation. You need a painkiller. Bad.

You go to the cabinet in the bathroom, but not for a bottle of pills. Instead, you open the cabinet and pick up a tiny remote control. You press a button, and the LED you had implanted in your brain just hours ago washes your augmented neuroreceptors with light. The pain fades, and then, euphoria.

This vision of the future of drugs could one day become a reality. Researchers at the University of Washington injected an opiate receptor in a mouse's brain—a specific neuron that is thought to disinhibit dopamine levels—with a light-sensitive protein. They then implanted an LED device the size of a hair near the receptor that, when turned on, stimulated the receptor modified with the protein and the associated reward response.


"By activating the receptors with light, we are presumably causing the brain to release more dopamine," said Dr. Michael Bruchas, an assistant professor of anesthesiology and of neurobiology, in a statement. "Rather than a drug such as morphine activating an opioid receptor, the light provides the reward."

According to the researchers, the power of the light could be dialed down or up, giving the mice a finely-tuned, light-induced high.

The mice were placed in two opaque black boxes. One chamber activated the light that stimulated the mice's neurons, and one didn't. The mice with the implants and optogenetically modified brains ended up spending more time in the former. As the researchers dialed the power of the light up, the mice showed an even stronger preference for the stimulating chamber.

This approach, outlined in a paper published in Neuron today, is referred to as optogenetics—augmenting neurons with proteins called opsins to respond to light. Previously, the technique has been used to give mice insta-boners, and flip the perception of a bad memory into a good one. And one day, the researchers say, it could be used in humans.

"It's conceivable that with much more research we could develop ways to use light to relieve pain without a patient needing to take a pain-killing drug with side effects," said Edward Suida, one of the paper's authors, in a statement.

But if a person with a history of addiction started to bask their brain in light instead of popping pills, could they get addicted to light too? While this question was not addressed in the paper, the researchers note that the mice in their trials appeared to really enjoy it. Clearly, some work still has to be done before the technique makes it to humans.