Nitric oxide (NO) acts as a neuronal messenger
which activates soluble guanylyl cyclase (SGC) in neighboring
cells and produces a wide range of physiological effects
in the central nervous system (CNS). Using immunocytochemical
and histochemical stains, we have characterized the NO/SGC
system in the rabbit retina and to a lesser extent, in
monkey retina. Based on staining patterns observed with
an antibody to nitric oxide synthase (NOS) type I and a
histochemical marker for NADPH diaphorase, a metabolic
intermediate required for NOS activity, three major classes
of neurons appear to generate NO in the rabbit retina.
These include two subclasses of sparsely distributed wide
field amacrine cells, rod and cone photoreceptors, and
a subpopulation of ganglion cells. Equivalent cell populations
were labled in monkey retina. An antibody to SGC (tested
only in rabbit retina), labeled large arrays of cone photoreceptors
in the outer nuclear layer, both amacrine and bipolar cells
in the inner nuclear layer (INL), as well as populations
of neurons in the ganglion cell layer. These data suggest
that the ability to generate NO is restricted to relatively
few neurons in the inner retina and to photoreceptor cells
in the outer retina; while presumptive target cells, containing
pools of SGC, are widespread and form contiguous fields
across the inner and outer nuclear layers (ONL) as well
as the ganglion cell layer.