Opioid receptor research
NIH-funded researchers have for the first time determined the crystallized structure of several opioid receptors involved in pain and mood regulation. Scientists predict that a better understanding of how drugs interact with these receptors could be used in the development of less addictive painkillers.
Kern: Athletes often refer to a high that they experience when pushing their bodies beyond normal limits. Dr. Jean Chin is a program director at the National Institute of General Medicinal Sciences at NIH. She says it's opioid receptors that are responsible for generating that other-worldly sensation.
Chin: The runner's high that you hear about. When people exercise they feel really good afterwards and that's because of the release of endorphins, and endorphins actually bind to these opioid receptors.
Kern: Opioid receptors are proteins imbedded in the membranes of certain cells in the brain, spinal cord, and digestive tract. Specific drugs can bind or stick to these receptors to start biochemical processes involved in mood and pain regulation.
Chin: And so what that means is that the endorphins are released and then they tickle these opioid receptors or we'll call them OR for short, and then they stimulate what they call euphoria or feeling good, and so it elevates your mood and they are also important in reducing pain perception.
Kern: The body's ability to naturally dull pain through the release of endorphins is important for athletes when pushing their bodies to extremes, but opioid receptors also bind several man-made drugs such as morphine and codeine that are prescribed to people suffering from debilitating pain. Though highly effective, these opiate-based drugs can quickly become addictive. In fact, the illicit drug, heroin, is a derivative of morphine and similarly binds to opioid receptors.
Chen: These outside things like morphine and heroine, they make you feel so good you want to keep on doing it and so then it becomes addictive. And so that's why it's important to understand how these different agents, whether they're uppers or downers or painkillers or whatever, how they interact with what we call these opioid receptors or ORs.
Kern: Recently, several NIH-funded researchers have made significant strides in understanding these interactions by finding a way to crystallize opioid receptors so that they can then take pictures of them. There are currently four known opioid receptors and while they all bind similar drugs, they do so with different strengths. Dr. Chin says these tiny differences can help researchers understand why some drugs prefer to bind to a specific class of opioid receptors.
Chin: Now they can start to compare, contrast, see how one works differently, why one family, one type of receptor binds this kind of ligand or morphine and another one only binds or prefers to bind like to endorphins and so forth. So these all have important implications in pain relief because they're analgesics so they lessen your pain. And some of them can sedate you. Some of them will elevate your mood. And because most of them are in the brain, that controls a lot.
Kern: Though the new pictures provide valuable information, Dr. Chin says they're still somewhat limited.
Chin: A picture is worth a thousand words. Everyone says that and it's really true. I think that it's a really terrific start, but we have to keep in mind that it's only one picture. What you really want is a movie. And so this is one state and so you want to see the whole thing from active form all the way through to the inactive form.
Kern: Given these recent advances in opioid receptor research, Dr. Chin is hopeful that scientists will eventually be able to develop less addictive painkillers.
Chin: Once they learn more about the mechanisms of binding, I think they'll be able to enable to design better drugs or ligands and also with fewer side effects so that if you want a painkiller you want only a painkiller, not one that will give you highs like morphine. So you want to be able to restrict any future drug ligands to what you want it to do.
Kern: For more about opioid receptor research, visit www.nigms.nih.gov. For NIH Radio, this is Margot Kern— NIH...Turning Discovery Into Health®
About This Audio Report
Reporter: Margot Kern
Sound Bite: Dr. Jean Chin
Topic: opioid receptors, opiates, endorphins, runnerís high, morphine, codeine, heroin, addiction, pain-killer, analgesic
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