Since nerve cell axons in the mature central nervous system do not regrow, neurologists have no way of fully treating paralysis due to injury. “About a hundred years ago, people started asking why it was impossible to get the axon to regenerate upon injury,” said Zhigang He, Harvard Medical School assistant professor of neurology at Children’s Hospital. Now, in two separate studies led by He, researchers at Harvard Medical School have identified a novel inhibitor of axon regeneration and discovered that the protein and two other known inhibitors function by binding to the same receptor. The research may facilitate development of drugs to block the receptor, allowing axons to regenerate and forming new therapies for people who have suffered injury to their central nervous system. One study was published online in the June 16, 2002 issue of Nature; the other appeared in the July 18, 2002 Neuron.