PORTLAND, Ore. -- A new treatment helped rats fight a disease similar to multiple sclerosis, and researchers say they will begin trials of the same treatment next month with 10 multiple sclerosis patients.

Doctors treated the rats with a protein fragment, or peptide, that induced the rats' immune systems to fight the disease, called experimental autoimmune encephalomyelitis.

Arthur Vandenbark and Halina Offner, researchers at the Portland Veterans Administration Medical Center, and George Hashim of St. Luke's Roosevelt Hospital in New York, published their findings in yesterday's Science magazine.

Vandenbark said improvements were seen in the rats within 48 hours after the peptide was administered. The rat disease, he added, produces symptoms similar to those of multiple sclerosis.

Multiple sclerosis is a disease of the nervous system. It can cause loss of muscle control, among other symptoms. One theory holds that multiple sclerosis occurs when the body's disease-fighting immune system mistakenly attacks nerve tissue in the brain and central nervous system.

The disease afflicts about 250,000 Americans, generally between the ages of 20 and 40. The cause is unknown, and so far no effective treatment has been discovered.

Patricia O'Looney, spokeswoman for the National Multiple Sclerosis Society in Washington, said the studies were exciting but "there is still a lot of work that needs to be done."