May 11, 2005 -- -- As part of his research, Dr. Jeff Mogil scoops up lab mice, one at a time, into specially designed cardboard and cloth pockets and holds each of them over a vat of hot water.
The mice don't seem to have a problem getting in the pockets, Mogil said. "It's dark and smelly in there."
But the pockets aren't quite big enough to hold the entire mouse. The tail hangs outside -- allowing Mogil to dip the tail into the 120-degree Fahrenheit water. Then he measures how long it takes for the mouse to flick its tail out.
Each mouse takes a different amount of time to react. And Mogil, a professor of pain studies at McGill University in Montreal, is trying to find out why.
Scientists have long recognized that all living things, from lab mice to human beings, have a range of pain sensitivity, and they're starting to discover the genetic basis of these differences. Doctors are on the cusp of a revolution in pain relief, they say.
Today, patients undergoing surgery get painkillers in a standard dosage mainly determined by body weight. But "there may be a point in time when we may be able to tell which patient responds to which type of pain medicine," said Dr. Sunny Anand, director of the Pain Neurobiology Laboratory at Arkansas Children's Hospital in Little Rock.
A patient could get a regimen of painkillers that will take into account his or her age, sex and pain threshold, and compensate for any side effects or possible predisposition to addiction.
"I don't think it's science fiction," Anand said. "Within the next five years we will be there."
There has already been some progress in understanding the genetic basis of pain. One of the primary areas of discovery has been the most fundamental: the difference between men and women.
Many scientists believe that male and female brains differ in architecture, and consequently, "some of the genetic differences that create sex brain differences may make pain vulnerability different," said Dr. Lonnie Zeltzer, director of the pediatric pain program at UCLA Mattel Children's Hospital.