Comparison of the Nitric Oxide / cGMP Signal Transduction System in the Turtle and Salamander Retinas

Abstract

Abstract: : Purpose:In retina, nitric oxide (NO) and/or cGMP have been shown to function in every retinal cell type. Although many aspects of these pathways have been analyzed in diverse species, only in turtle retina has the entire NO/cGMP signal transduction system has been well characterized using a combination of NO imaging and nitric oxide synthase and cGMP immunocytochemistry. As the salamander is such a widely used retinal preparation, we wanted to use previously established techniques to fully characterize its NO/cGMP signal transduction system and compare it to the turtle retina. Methods:Nitric oxide production was measured in vitro using retinal slices that were loaded with the NO sensitive dye, diaminofluorescein diacetate, DAF 2-DA. Nitric oxide synthase and NO-stimulated increases in cGMP were examined using immunocytochemical methods. Results:The NO/cGMP signal transduction systems were very similar in both turtle and salamander retina. In both species, NOS immunoreactivity was present in photoreceptor, amacrine, bipolar and horizontal cells. NO-stimulated increases in cGMP were present in amacrine, bipolar and ganglion cells in both turtle and salamander. Finally, in both species the NO production seen with DAF 2 could be colocalized with NOS. Conclusion:The NO/cGMP signal transduction system is robust and well conserved between turtle and salamander. Either of these species is well suited for future studies of these signal transduction pathways.

Keywords: 491 nitric oxide • 556 retina: neurochemistry • 580 signal transduction