NEW ORLEANS, NOV. 13 -- Laboratory rats with nerves cut at the spine have been made to feel again, a breakthrough that may someday let doctors help people with spinal injuries, a researcher says.

"We believe we really have regeneration into the spinal cord," the first time this has been shown, said Dr. Jerry Silver of Case Western Reserve University in Cleveland.

It is widely held that the injured spinal cord cannot be repaired. Silver is working with the nerve that carries feeling from a rat's right hind leg to the spinal cord.

Silver, a neuroscientist with a doctorate in anatomy, is to present his findings Monday to a symposium at the Society for Neuroscience meeting here.

He said he and his colleagues began by cutting roots of the sciatic nerve. Cutting the root just outside the fifth vertebra has effects much like those when a ruptured spinal disc crushes that root of the sciatic nerve, he said. Toes can be moved but have no feeling.

Silver said the rats' sciatic nerve roots were cut at the fourth and sixth vertebra and crushed at the fifth. Then cells called astrocytes were used to try to repair damage at the fifth vertebra.

In embryros, astrocytes build what Silver described as highways for the long fibers through which information goes to and from a nerve cell. But in adults, he said, they build scar tissue that blocks off damaged nerve cells.

Nobody knows why or how this change occurs, he said.

He said his team made bridges from a new porous polymer coated with glia -- the long nerve fibers -- of astrocytes from rat embryos.

He said most animals regain some feeling within a week. But those treated with embryonic astrocyte glia seem to come much closer to normal.

Of 44 rats tested, he said, 13 were treated with fetal astrocytes. All 13 regained feeling.