Stages of axonal regeneration following optic nerve crush in goldfish: contrasting effects of conditioning nerve lesions and intraocular acetoxycycloheximide injections.
The progress of axonal outgrowth after a crush lesion of the goldfish optic nerve can be determined by examining longitudinal silver-stained sections at selected intervals. The outgrowth of leading axons proceeded at 0.46 mm/day after an initial delay of 4.2 days. Outgrowth can be rapidly characterized by differentiating among a series of qualitatively different stages. In the sprouting (S) phase of regeneration, stage S1 is defined by the presence of isolated axonal sprouts reaching into the crush zone, and stage S2 by bundles of sprouts in the crush zone. In the elongation (E) phase of regeneration, stage E1 is defined by bundles that bridge the crush zone, stage E2 by bundles that reach the optic chiasm, and stage E3 by bundles that reach the level of the hypothalamus. During normal regeneration, stage E2 was attained 7-9 days after the crush (testing lesion), and stage E3 at 11 days. However, if the testing lesion had been preceded by a similar (conditioning) lesion 2 weeks earlier, stage E2 was reached at 3 days and stage E3 at 5 days. Conversely, when a protein synthesis inhibitor (acetoxycycloheximide) was injected into the right eye daily from the 5th through 9th day after a testing lesion, the injected side lagged 1-2 stages behind the contralateral control side in nerves examined on the 10th day.
D000818:Animals; D003513:Cycloheximide / Q000031:analogs & derivatives* / Q000494:pharmacology; D003530:Cyprinidae / Q000502:physiology*; D006054:Goldfish / Q000502:physiology*; D009416:Nerve Regeneration / Q000187:drug effects; D009900:Optic Nerve / Q000473:pathology / Q000502:physiology*; D020221:Optic Nerve Injuries
D003513:Cycloheximide; C004434:acetoxycycloheximide