EFFECT OF OPTIC-NERVE LESIONS AND INTRAOCULAR COLCHICINE ON CELL-PROLIFERATION IN THE GERMINAL ZONE OF THE OPTIC TECTUM AND IN THE TORUS-LONGITUDINALIS IN THE GOLDFISH

Postembryonic development of the optic tectum occurs in part through proliferation of cells in the germinal zone located at the caudal edges of each lobe. Autoradiography experiments by others have shown that [3H]thymidine labeling in the germinal zone is decreased following optic nerve crush or enucleation and restored above normal levels during optic nerve regeneration. The present autoradiography experiments examined the relationship between retinal innervation and the rate mitotic activity in the tectum germinal zone and in the torus longitudinalis. The fish received optic nerve crush to temporarily deafferent the tectum, enucleation for permanent deafferentiation, or an intraocular injection of 0.01-1.0 μg of colchicine to reversibly inhibit axonal transport in the optic nerve. Thymidine labeling in the tectum germinal zone showed that nerve crush resulted in decreased mitotic activity in most fish within 6 days followed by recovery by 21 days; enucleation decreased mitotic activity more uniformly and for more than 42 days with recovery by 84 days postaxotomy; colchicine produced a dose-dependent inhibition of mitotic activity which was reversed by 42 days postinjection. Axonal transport was restored by 42 days postinjection. In the torus longitudinalis, nerve crush produced a brief increase in mitotic activity followed by a return to a normal; enucleation and colchicine resulted in a lasting decrease in mitotic activity and atrophy indicating a loss of cells or neuropil. The data are consistent with the proposal that cell proliferation in the tectum germinal zone is stimulated by the accretion of fibers from developing retinal ganglion cells. Axonal transport of cellular materials in mature retinal fibers may also be involved. The results further suggest that the torus longitudinalis undergoes postembryonic development apace the optic tectum, and that its growth, like that of the tectum, is stimulated by the eye. © 1990.