The Differences Between Cholera Toxin Subunit B And Fluoro-gold In Retrograde Tracing Of Retinal Ganglion Cells

Objective: To compare differences between Cholera toxin subunit B(CTB) and Fluoro-Gold(FG) in retrograde tracing of retinal ganglion cells(RGCs) in SD rats.Methods: 22 adult female SD rats(210-240g) were chosen to compare differences between CTB and FG by injecting two tracers into bilateral superior colliculus and lateral geniculate nucleus. The rats surviving 1 week or 2 weeks after CTB injection were denominated CTB-1w(n=5 rats, 10 eyes) or CTB-2w(n=5 rats, 10 eyes); The rats surviving 1 week or 2 weeks after FG injection were designated FG-1w(n=5 rats, 10 eyes) or FG-2w(n=5 rats, 10 eyes); the remaining 2 rats as control group were injected with a mixed solution of CTB and FG. 1 week or 2 weeks later, all rats were killed. Their retinas, brains and optic nerves were collected. Parameters including the mean density of RGCs, the mean length and mean amount of RGCs processes, the diffusion area of tracers were calculated by Image-Pro Plus 6.0. All data were statistically analyzed by IBM SPSS Statistics 22.0 and the statistical significance was set at p<0.05.Results:Both FG-1w and FG-2w displayed more labeled RGCs and more diffusion area of tracers than CTB-1w and CTB-2w(each p<0.001). Also, CTB-2w showed a greater RGCs number and diffusion area of tracers when comparing to CTB-1w(each p<0.001), but there was no distinction between FG-1w and FG-2w(each p>0.05). As for the mean length and mean amount of RGCs processes, both CTB-1w and CTB-2w showed longer RGCs processes and more amount of RGCs processes than FG-1w and FG-2w(each p<0.001),no difference was found neither between CTB-1w and CTB-2w,nor between FG-1w and FG-2w(each p>0.05). In optic nerves, an obvious distinction was found that the optic nerves labeled by CTB were much clearer than FG labeled.Conclusion:(1)Both CTB and FG could successfully retrograde label the RGCs of SD rats in 1 week and 2 weeks.(2)CTB labeling showed a superiority in outlining the morphology of RGCs, while FG labeling displayed a more thorough labeling of RGCs number.