Abstract
We examined whether elevation of cAMP or activation of macrophage can make crushed axons of retinal ganglion cells (RGCs) to regenerate into the cat optic nerve (OpN). The left OpN was crushed with a 6-0 thread pulled with 0.2 N, 60 sec (microcrush). Forskolin (30 min before OpN crush), zymozan (60 m after the crush), or oxidized galectin-1 (60 m after the crush), was injected into the vitreous. At day 12, WGA-HRP was injected to anterogradely label regenerated axons. On day 14, deeply anesthetized cats perfused with fixative. The excised OpN was longitudinally cut on a cryostat, labeled axons were visualized with TMB reaction. Number of Regenerated Axons. The OpN with saline-injection (control) contained very few labeled axons elongating beyond the crush site, whereas OpN with injections of forskolin (0.1 mg), zymozan (50 μg), or galectin (0.5-1000 ng) had many labeled axons elongating beyond the crush site. Mean numbers (N=2 to 4) of labeled axons of 0.5 mm or longer were 24 (control), 341 (forskolin 0.1 mg), 275 (galectin 0.5 ng), 2755 (galectin 100 ng), 1355 (galectin 1000 ng), 601 (zymozan), respectively. Similar tendency was found in the mean axon numbers at 1.0 mm. Longest Axons. We measured length of the longest axons, and found no statistically significant difference among values from experiments. Crushed axons of adult cats regenerated into the OpN when a macrophage activator was injected or intracellular cAMP was elevated. The elongation rate of regenerated axons was estimated as less than 1 mm/ wk. [Jpn J Physiol 55 Suppl:S156 (2005)]
