Failure to restore vision after optic nerve regeneration in reptiles: interspecies variation in response to axotomy.
J Comp Neurol
; 478(3): 292-305, 2004 Oct 18.
Article
in En
| MEDLINE
| ID: mdl-15368531
ABSTRACT
Optic nerve regeneration within the reptiles is variable. In a snake, Viper aspis, and the lizard Gallotia galloti, regeneration is slow, although some retinal ganglion cell (RGC) axons eventually reach the visual centers (Rio et al. [1989] Brain Res 479151-156; Lang et al. [1998] Glia 2361-74). By contrast, in a lizard, Ctenophorus ornatus, numerous RGC axons regenerate rapidly to the visual centers, but unless animals are stimulated visually, the regenerated projection lacks topography and animals remain blind via the experimental eye (Beazley et al. [2003] J. Neurotrauma 201263-1269). V. aspis, G. galloti, and C. ornatus belong respectively to the Serpentes, Lacertidae, and Agamidae within the Eureptilia, the major modern group of living reptiles comprising the Squamata (snakes, lizards, and geckos) and the Crocodyllia. Here we have extended the findings on Eureptilia to include two geckos (Gekkonidae), Cehyra variegata and Nephrurus stellatus. We also examined a turtle, Chelodina oblonga, the Testudines being the sole surviving representatives of the Parareptilia, the more ancient reptilian group. In all three species, visually elicited behavioral responses were absent throughout regeneration, a result supported electrophysiologically; axonal tracing revealed that only a small proportion of RGC axons crossed the lesion and none entered the contralateral optic tract. RGC axons failed to reach the chiasm in C. oblonga, and in G. variegata, and N. stellatus RGC axons entered the opposite optic nerve; a limited ipsilateral projection was seen in G. variegata. Our results support a heterogeneous response to axotomy within the reptiles, each of which is nevertheless dysfunctional.
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Collection:
01-internacional
Database:
MEDLINE
Main subject:
Optic Nerve
/
Vision, Ocular
/
Axotomy
/
Nerve Regeneration
Type of study:
Prognostic_studies
Limits:
Animals
Language:
En
Journal:
J Comp Neurol
Year:
2004
Document type:
Article
Affiliation country:
Australia