The Effect of Cycloheximide and Ganglioside GM1 on the Viability of Retinotectally Projecting Ganglion Cells Following Ablation of the Superior Colliculus in Neonatal Rats

Abstract

The time-course and extent of death of retinal ganglion cells (RGCs) following ablation of the superior colliculus (SC) in neonatal Wistar rats has recently been described [Harvey, A. R. and Robertson, D. (1992) J. Comp. Neurol., 325, 83-94]. Normal and pyknotic nuclei of retinotectally projecting ganglion cells were visualized using the fluorescent retrograde tracer diamidino yellow (DY), which had been injected into the SC at P2 (day of birth = P0), 2 days prior to tectal removal. The present report sets out to determine whether cycloheximide, an inhibitor of protein synthesis, or ganglioside GM1 reduced this lesion-induced RGC death. All surgery was carried out under ether anaesthesia; DY was injected into the left SC at P2 and the injected area was removed at P4. Cycloheximide (20-500 ng) was injected into the vitreous chamber of the right eye immediately after the lesion and again 11-12 h later. In some rats, cycloheximide administration was delayed until 12 h after the SC ablation. Control rats received SC lesions alone or lesions plus sham eye injections of saline. Different doses of GM1 were applied i.p. or intraocularly. Rats were perfused 24 h after the SC lesion, at the time of peak RGC death. Retinae of lesion only or sham eye injected rats contained approximately 11% pyknotic RGCs and the density of normal RGCs was approximately 3400/mm2. The rate of pyknosis in cycloheximide treated retinae was reduced to approximately 3%. Normal RGC density in these retinae was approximately 5500/mm2, similar to that found in retinae of unlesioned animals.(ABSTRACT TRUNCATED AT 250 WORDS)