Tropic factors in reactive mammalian central nervous system tissue.

Previous studies suggest that distal stumps of transected peripheral nerves contain diffusible factors which can attract/support axonal regeneration over distances of several mm in vivo. The present experiments were undertaken to determine if this is so for distal regions of traumatized central (i.e., optic) nerves. Proximal stumps of transected rat sciatic nerves were inserted into the single inlet ends of 6 mm long Y-shaped Silastic implants. Alternative 'lures' were attached to the paired outlets, the ability of these lures to attract/support regeneration of nerve fibers in their associated forks assessed 3.5 weeks postoperatively. Exclusive or preferential growth of nerve fibers occurred in implant forks associated with optic nerve grafts, of Elvax pellets containing homogenate obtained from previously crushed (reactive) optic nerves. Grafts of tendon, as well as homogenate from unoperated optic nerve had no effect. Results suggest that, with respect to the assay used, degenerating optic nerve tissue contains factor(s) which can attract/support regenerating nerve fibers.