Tetrodotoxin inhibits the formation of refined retinotopography in goldfish.

One optic nerve of mature goldfish was crushed in the orbit and allowed to regenerate. During regeneration impulse activity was eliminated by periodic intraocular injections of tetrodotoxin (TTX). At 32-104 days, the retinotopography of the retinotectal projection was measured autoradiographically by intraocular [3H]proline injections simultaneous with either small (10-20 degrees sector) or half retinal mapping lesions. TTX had no effect on the time-course and quality of the regeneration of gross topography seen with half retina mapping, but indefinitely inhibited higher order (refined) retinotopography normally seen by 2 months with retina sector mapping.