Locally administered nerve growth factor suppresses ginsenoside Rb1-enhanced peripheral nerve regeneration.

A high-dose of nerve growth factor (NGF) mixed with ginsenoside Rb1 (GRb1) was encapsulated by collagen and placed in silicone rubber chambers, which were used to repair dissected Sprague-Dawley rat sciatic nerves with 15 mm gaps. Six weeks after surgery, no axons or Schwann cells were seen in these chambers. By comparison, nerves treated with collagen-GRb1 alone had regenerated axons and Schwann cells in their endoneurial areas. We suggest that excessive NGF may not promote but, rather, suppress developing nerves.