Send to:

Choose Destination
See comment in PubMed Commons below
Invest Ophthalmol Vis Sci. 1999 Nov;40(12):2884-91.

Isoforms of nitric oxide synthase in the optic nerves of rat eyes with chronic moderately elevated intraocular pressure.

Author information

  • 1Department of Ophthalmology and Visual Sciences, Washington University School of Medicine, St. Louis, Missouri 63110, USA.



To investigate the hypothesis that nitric oxide (NO) in the optic nerve heads of rats with chronic moderately elevated intraocular pressure (IOP) contributes to neurotoxicity of the retinal ganglion cells, the presence of the three isoforms of nitric oxide synthase (NOS) was determined in the tissue.


Unilateral chronic moderately elevated IOP was produced in rats by cautery of three episcleral vessels. Histologic sections of optic nerves from eyes with normal IOP and with chronic moderately elevated IOP were studied by immunohistochemistry and by immunoblot analysis. Polyclonal antibodies to NOS-1, NOS-2, NOS-3, and glial fibrillary acidic protein (GFAP) were localized with immunoperoxidase.


In the optic nerve of rat eyes with normal IOP, NOS-1 was constitutively present in astrocytes, pericytes and nerve terminals in the walls of the central artery. NOS-2 was not present in eyes with normal IOP. In these eyes, NOS-3 was constitutively present in the vascular endothelia of large and small vessels. Rat eyes treated with three-vessel cautery had sustained elevated IOP (1.6 fold) for at least 3 months. In these eyes, no obvious changes in NOS-1 or NOS-3 were noted. However, at time points as early as 4 days of chronic moderately elevated IOP, NOS-2 appeared in astrocytes in the optic nerve heads of these eyes and persisted for up to 3 months. Immunoblot analysis did not detect differences in NOS isoforms.


The cellular distributions of constitutive NOS isoforms in the rat optic nerve suggest physiological roles for NO in this tissue. NOS-1 in astrocytes may produce NO as a mediator between neighboring cells. NO, produced by NOS-1 in pericytes and nitrergic nerve terminals and by NOS-3 in vascular endothelia, is probably a physiological vasodilator in this tissue. In eyes with chronic moderately elevated IOP, NOS-2 is apparently induced in astrocytes. The excessive NO production that is associated with this isoform may contribute to the neurotoxicity of the retinal ganglion cells in eyes with chronic moderately elevated IOP.

[PubMed - indexed for MEDLINE]
PubMed Commons home

PubMed Commons

How to join PubMed Commons

    Supplemental Content

    Full text links

    Icon for Silverchair Information Systems
    Loading ...
    Write to the Help Desk