In new research published online April 30 in the journal Neuron, neuroscientists at Washington University School of Medicine in St. Louis report that they have found a way to activate opioid receptors with light. The scientists melded the light-sensing protein rhodopsin to key parts of opioid receptors to activate receptor pathways using light. They were also able to affect the behavior of mice by injecting the receptors into the brain, using light instead of drugs to stimulate a reward response. With further investigation, the team hopes to develop ways to use light to relieve pain, a line of discovery that also could lead to better pain-killing drugs with fewer side effects.
As a precursor to that achievement, the researchers are attempting to learn the most effective ways to activate and deactivate the opioid receptor’s pathways in brain cells. Michael Bruchas, PhD, the study’s principal investigator, explained that working with light rather than pain-killing drugs makes it much easier to understand how the receptors function within the complex array of cells and circuits in the brain and spinal cord. This understanding has been complicated by the fact that opioid receptors have multiple functions in the body. In this research, by combining the rhodopsin protein, which senses light in the eye’s retina, with a Mu opioid receptor, the team were able to build a receptor that responds to light in exactly the same way that standard opioid receptors respond to pain-killing drugs. Read more about the research findings here.