A quantitative study of regenerative sprouting by optic axons in goldfish

Regenerative sprouting by optic axons of goldfish was examined distal to the site of a crush lesion. Normally, optic nerves of large goldfish contain approximately 2 × 105 myelinated axons. The number of axonal processes in the nerve distal to the lesion increases fourfold during the first 3 months postoperatively and then returns toward preoperative numbers after 3 months. The excess number of axonal processes therefore persists several months beyond the return of visual function. The magnitude and time course of regenerative sprouting by goldfish optic axons is similar to that reported for mammalian and nonmammalian peripheral axons.