Retinal ganglion cell death is not prevented by application of tetrodotoxin during optic nerve regeneration in the frog Hyla moorei.

Following extracranial optic nerve crush in the adult frog Hyla moorei, regeneration takes place to restore topographically organised visual projections, despite partial depletion of the retinal ganglion cell population. In the present study, the right optic nerve was crushed and tetrodotoxin (TTX) repeatedly injected into the right eye to abolish electrical activity mediated by sodium channels in ganglion cell axons. At 70-78 days post-crush, the number and distribution of live cells in the ganglion cell layer were assessed from cresyl violet-stained wholemounts. After regeneration, cell numbers in TTX-treated animals fell by a mean of 32.6% in comparison with their unoperated partner retinae. This value was very similar to the 32.4% mean fall found after regeneration for animals receiving no injections of TTX. Furthermore, distributions of surviving cells were comparable for the two groups. We conclude that sodium-mediated electrical activity within retinal ganglion cells does not control the extent or pattern of their death during optic nerve regeneration.