Narrator: This is Science Today. Morphine is one of the most effective treatments for chronic pain. But long-term users tend to develop a tolerance for the drug, forcing doctors to prescribe higher doses. Now, scientists at the University of California, San Francisco have made a discovery that could lead to better long-term pain relief. Researcher Jennifer Whistler compares morphine tolerance to a light bulb that's always on.Whistler: And as a consequence of that the cells put on dark glasses. The drug is still there, it should be effective, it's still effective at the receptor but the cells don't feel it anymore because they've put their dark glasses on. So what we wanted to do is prevent the cells from putting on their dark glasses.
Narrator: Whistler gave test subjects a tiny dose of another opiate to keep their cells from developing a tolerance for morphine. In higher doses, opiates like methadone are too addictive to be used for pain relief.
Whistler: What we're hoping is that we can use them at a very low dose where they'll have no effect on their own. But if we use them at a very low dose in combination with morphine, we can enhance the efficacy of morphine because we'll prevent the development of tolerance.
Narrator: For Science Today, I'm Larissa Branin.