Leech may hold key to neural regeneration.

The medicinal leech, a worm-like creature once used by doctors to bleed patients, is being examined to draw clues on how a common protein may help promote neural regeneration. Biologist Christie Sahley and research assistant Orie Shafer of Purdue University, West Lafayette, Ind., have found that nitric oxide synthase (NOS) is activated when parts of the nerve cell are damaged in the medicinal leech. a three-inch-long invertebrate known for the ability to regenerate its neural connections.

"Our study shows that NOS in the leech is activated at the site of injury within minutes after axons are severed, and it remains active well beyond 48 hours after the injury," Sahley explains. Axons are the long "arms" of a nerve cell that carry impulses away from the cell body toward a target cell.

Because the NOS found in leeches is very much like the human NOS, it may serve a similar function in both species, she says. "Nerve cells in leeches are basically identical in structure and function to those in more complicated systems such as humans. But for some reason, nerve regeneration in higher systems is not complete. By analyzing how nerves regenerate in a simple system, we may find clues to facilitate...