Pain can be more than a symptom of injury

May 23, 1999|By Rosie Mestel, | Rosie Mestel,,los angeles times

Recent discoveries could change the way scientists and doctors view pain.

"Pain is not just a symptom of an injury," says Allan Basbaum, chairman of the department of anatomy at the University of California, San Francisco. "Under some conditions, it's really a disease of the nervous system."

What Basbaum is saying is that pain nerves, when we're injured, seem to subtly change. And those changes, if they stick around, can set people up for longer-term misery -- misery that might be avoided if the initial pain were nipped in the bud.

Such nipping should be easier in the future. For years, pain management has relied largely on two groups of drugs: opioids, derived from morphine; and nonsteroidal anti-inflammatory drugs (NSAIDs), a class of painkillers that includes aspirin and ibuprofen. Both groups have side effects, such as addictive potential and constipation for opioids, and stomach irritation for NSAIDs. And they don't work for all types of pain.

Today, though, scientists have homed in on a dizzying array of molecules our bodies use in the pain response. Many of them offer different ways to interfere with the pain pathway.

People vary greatly in how much they feel an incoming pain sensation. Certain cultures accept pain more readily. Certain people just don't let pain get to them as easily. If people are focused on some tricky task, or if they're excited, they'll feel pain less.

Our body's pain-fighting system is responsible. Sometimes, when the brain's got other pressing things to think about, it shushes the pain signals, using several chemicals (including our body's natural painkillers, endorphins) to relay its "Be quiet!" message back down the spinal cord.

What makes pain persist for years? With a condition like arthritis, the answer's simple: The injury doesn't leave, so the pain doesn't leave. Sometimes, though, pain remains even after an injury has healed. In those cases, pangs are often caused by changes wrought on the nervous system.

Some of those changes made sense when the tissue damage was there. For instance, pain sensitivity goes way up at the site of an injury -- and that's useful. If things that didn't hurt before -- such as simply walking -- now become torture, you're more likely to keep weight off that sprain and let it heal.

But sometimes, nerves remain changed long after visible signs of healing. What this means, say pain scientists, is that treating pain promptly could ward off trouble down the road. "There's no reason to be stoic," Basbaum says. "All the data -- ours and others' -- says that the persistence of pain is bad."

The list of ways the body can turn rogue and make you hurt goes on and on. Sometimes, damage from a stroke can make the brain think the body is hurting somewhere when it's not. Sometimes, we can end up feeling pain at a different site from the actual source of a pain.

But luckily, the list of new drugs being explored is getting longer, though the ones found to work may take years to come to market.

"As we learn more about the biology of pain, our drugs become more specific, and hopefully they'll do just the good things, and not the bad things, that the old drugs did," says Dr. Jack Berger, assistant professor of anesthesia at the University of Southern California.

Pub Date: 05/23/99

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