--------Study: Procedures on Preemies May Boost Sensitivity to Pain
　　By Paul Recer
　　The Associated Press
　　W A S H I N G T O N, July 28?Doctors long have been uncertain just how much pain premature infants feel during medical therapy. A new study in rats suggests that the effects of that pain may last a lifetime.
　　In a study appearing today in the journal Science, researchers at the National Institutes of Health found that painful trauma, like that caused by medical procedures on premature infants, caused newborn rats to become much more sensitive to pain as they grew older.
　　More Pain Nerve Cells
　　The reason, said NIH researcher M.A. Ruda, is that pain causes the developing nervous system of the very young to grow more of the nerve cells that carry the sensation of pain to the brain.
　　“We found that there are more nerve endings that fire and transmit the information,'?said Ruda, first author of the study. “These animals later were more sensitive and had a greater response to pain.'? 　　Ruda said the study only suggests what may happen in premature infants.

Studies Have Human Implications
　　Medical science is in the midst of an intense effort to understand how the nervous system develops and how the growth of nerve tissue is affected by stimulation such as pain. The research has a direct bearing on efforts to save and improve the lives of infants born prematurely, before the normal 40-week gestation.
　　Survival of babies born up to 15 weeks premature is now not unusual, but it requires a major medical effort and many painful procedures, including countless needle sticks, breathing tubes and even surgery.
　　Dr. Patricia A. McGrath, a pain researcher and professor of pediatrics at the University of Western Ontario, said that 10 years ago “there was a real belief that the pain system in premature babies was not developed and these infants would really not feel as much pain.'?

Choosing Pain vs. Anesthetics
　　More importantly, McGrath said, doctors worried that premature infants given powerful anesthetics “would not be able to clear the drug as well as older infants.'?The choice sometimes was between skipping anesthesia during lifesaving surgery or no therapy. Most doctors chose life and hoped that the pain caused no lasting effect.
　　But Ruda said that the study in rats suggests there is a lasting effect.
　　In the study, Ruda and her colleagues injected an irritant that causes pain into the left rear paw of day-old rats. Lab rats at that age are in the same development stage as human babies born at 25 weeks of gestation.
　　The paws were sore for several days and then healed.

Test Animals More Pain Sensitive
　　Later, when the rats were grown, the researchers tested their perception of pain by seeing how fast the animals would withdraw from a hot surface. Their reaction time was compared with that of control rats that had not been treated.
　　Ruda said the treated rats reacted to the heat about twice as fast as the control rats.
　　When the heat test was administered on the right, or untreated paw, of the test rats, they reacted just as did the control rats. This suggested that the pain early in life had made the treated paw permanently more sensitive to pain.
　　Microscopic examination of nerves in the animals showed why, Ruda said.
　　In the treated paw of the rats, there were more nerve circuits to carry pain stimuli to the brain, said Ruda.
　　Ruda said other studies have shown that premature babies tend to report more pain in their childhood years and their parents report that these children’s pain response is greater than that of their siblings.
　　Dr. Jonelle C. Rowe, an NIH doctor who specializes in treating premature babies, said there may have been some babies in the past who had surgery without anesthesia, as Ruda claims, but that it was rare.

(From ABCNEWS.com)