Brain Research 883 (2000) 98–106 www.elsevier.com / locate / bres Research report Growing and regenerating axons in the visual system of teleosts are recognized with the antibody RT97 a b a a ´ Almudena Velasco , Marıa Julia Bragado , David Jimeno , Elena Caminos , a a a, * ´ ´ ´ Concepcion Lillo , Jose Aijon , Juan M. Lara a ´ ´ ´ Instituto de Neurociencias de Castilla y Leon, Departamento de Biologıa Celular y Patologıa, Universidad de Salamanca, E-37007 Salamanca, Spain b ´ ´ ´ Departamento de Fisiologıa, Universidad de Alcala de Henares, Madrid, Spain Accepted 2 August 2000 Abstract We have analyzed the immunolabeling with the antibody RT97, a good marker for ganglion cell axons in several species, in the normal and regenerating visual pathways of teleosts. We have demonstrated that RT97 antibody recognizes several proteins in the tench visual system tissues (105, 115, 160, 200, 325 and 335 kDa approximately). By using immunoprecipitation and Western blot we have found that after crushing the optic nerve the immunoreactivity to anti RT97 increased markedly in the optic nerve. In immunohistochemical analysis we also found a different pattern of labeling in normal and regenerating visual pathways. In normal tench RT97 is a good marker for the horizontal cells in the retina, for growing ganglion cell axons which run along the optic nerve from the retina to the optic tectum and of the axon terminals in the stratum opticum and stratum fibrosum and griseum superficiale in the optic tectum. After optic nerve crush, no immunohistochemistry modifications were observed in the retina. However, in accordance with Western blot experiments, in the optic nerve intensely stained groups of regenerating axons appeared progressively throughout the optic nerve as far as the optic tectum. We conclude that the antibody RT97 is an excellent marker of growing and regenerating axons of the optic nerve of fish.  2000 Elsevier Science B.V. All rights reserved. Theme: Development and regeneration Topic: Regeneration Keywords: Fish; Neurofilaments; Optic nerve; Optic tectum; Retina 1. Introduction levels, in the axonal transport and in the cytoskeleton of the ganglion cell axons [13,17]. The retinas of some teleosts have two peculiarities with In relation to the cytoskeleton of fish retinal ganglion respect to other vertebrates: the retina grows throughout cells, different studies of the expression of the proteins of the life of the animal from a peripheral germinal zone [26] the neurofilaments, both in the normal state and after a continuously adding new neurons and axons of the gang- lesion [9,14,22,29], have been carried out. In mammals, lion cells and the retinal ganglion cells are capable of principal neurofilament proteins have been classified into regenerating their axons and restoring vision after a lesion three types according to their molecular weight: neuro- in the optic nerve [4,17,31]. During the growth and filament-light (NF-L), neurofilament-medium (NF-M) and regeneration processes important changes occur in the neurofilament-heavy (NF-H) [32]. In fish, differences in visual pathways, both at morphological and biochemical the composition of these proteins have been described in comparison to those of mammals. The predominant pro- teins of the neurofilaments of the goldfish optic nerve have a low molecular weight, such as gefiltin, a type IV *Corresponding author. Tel.: 134-923-294-500; fax: 134-923-294- neurofilament protein [15] and plasticin, a type III neuro- 549. E-mail address: rororo@gugu.usal.es (J.M. Lara). filament protein [14]. NF-M proteins have also been 0006-8993 / 00 / $ – see front matter  2000 Elsevier Science B.V. All rights reserved. PII: S0006-8993(00)02783-9