Toluidine blue-stained 1-μm-thick sections of intact sciatic nerves of control vehicle (A) and high-dose rhGDNF-injected (B) rats. In rhGDNF-injected animals, the myelinated fibers were widely separated and the intervening space contained an increased number of unmyelinated Schwann cells. Examples of Schwann cell nuclei are marked byarrows in B. A mitotic figure (arrow) in a Schwann cell in an rhGDNF-injected animal is shown among other Schwann cell nuclei (asterisks) in the inset (original magnification, 1000×).