Abstract
Unlike the mammals, the fish optic nerve can regenerate after nerve transection. Although the regenerating optic axons in goldfish can reach to the tectum 4-6 weeks after axotomy, the visual function restores just 4-6 months later. GAP-43 which is a 43 kDa growth associated protein, is localized in the growth cone. In order to study level and cellular localization of GAP-43 mRNA in the goldfish retina and tectum during optic nerve regeneration, we got a 639 bp cDNA fragment for goldfish GAP-43 by PCR amplification. Using this cDNA fragment, Northern blot and in situ hybridizations were performed in the goldfish retinas and tecta following optic nerve injury. In the retina, levels of GAP-43 mRNA started to increase 3-5 days, peaked 6.5-fold 10-20 days and rapidly decreased 4-fold by 30 days after nerve injury. The 4-fold increase of GAP-43 mRNA levels lasted 3-4 months and then gradually declined to the control level 5-6 months after injury. The change of GAP-43 mRNA levels was only localized in the ganglion cells. The levels of GAP-43 protein showed a similar expression pattern to that of the mRNA. In the tectum, the levels of GAP-43 protein increased 2.2 fold for a long time (20-100 days) after injury. The change of GAP-43 protein levels was localized in the tectal plexiform layers. These results strongly indicate that the time course of GAP-43 expression is well correlated with that of the recovery of fish visual function from the optic nerve injury. [Jpn J Physiol 55 Suppl:S167 (2005)]
