Neuronal nitric oxide synthase (nNOS) positive retinal amacrine cells are altered in the DBA/2NNia mouse, a murine model for angle-closure glaucoma

Purpose: To characterize retinal amacrine cell changes in eyes of DBA/2NNia (DBA) mice that develop an inherited angle-closure glaucoma. Methods: DBA and non-glaucomatous C57BL/6J mice of different age groups (2 to 23 months of age) were studied and compared. Morphologic investigations included NADPH-diaphorase staining of retinal whole mounts and fluorescence immunohistochemistry of cryosections with antibodies against neuronal nitric oxide synthase (nNOS), tyrosin hydroxylase (TH), gamma aminobutyric acid (GABA), and vesicular acetylcholine transporter (VAChT). Results: Immunohistochemistry of amacrine cell subpopulations in the retinae of DBA mice revealed no significant staining differences in the two mouse strains at all ages using antibodies against TH, GABA, and VAChT. However, staining with nNOS and NADPH diaphorase revealed significant differences between the DBA strain and the C57BL/6J mice. With the onset of elevated IOP and glaucoma beginning at around 6 months in the DBA mice, the total number of NOS positive amacrine cells continuously decreased from 1000 cells at 6 months of age down to 480 cells in animals older than 20 months of age, but did not decline in age-matched C57 mouse retinas. Conclusion: We previously described a parafoveal loss of nNOS positive amacrine cells in the monkey glaucoma model. The fact that there is also a significant decrease of nNOS amacrine cells in the glaucomatous mouse eye indicates a specific response of nNOS positive amacrine cells in glaucomatous retinopathy.