Light And Electron Microscopical Analysis Of Neuronal Nitric Oxide Synthase Neurons In The Macaque Monkey Retina

Abstract

Abstract: : Purpose:The aim of this study is to investigate the morphology and synaptic connectivity of nNOS immunoreactive neurons in the macaque monkey retina. Methods:Whole-mount preparations and 50 mm thick vertical vibratome sections were immunostained with an anti-nNOS antiserum. Colocalization of nNOS and GABA was examined. Synaptic connectivity of nNOS neurons in the IPL was examined by electron microscope. Results:Specific nNOS immunoreactivity was localized to two types, type 1 and type 2, of amacrine cells and a certain population of displaced amacrine cells. Type 1 cells had large-sized soma and their processes mainly stratified in strata 2 and 3 of the IPL, while type 2 cells had small-sized soma and their processes ramified in stratum 1. Labeled displaced amacrine cells ramified in strata 4 and 5 of the IPL. The density of type 1, type 2 and displaced amacrine cells was 265/mm₂, 40/mm₂ and 20/mm₂ in the mid-peripheral region of the retina. Double-label immunohistochemistry demonstrated that all nNOS-immunoreactive cells possessed GABA immunoreactivity. The nNOS-labeled amacrine cell processes received synaptic input from other amacrine cell processes and bipolar cell axon terminals in strata 1 to 4 of the IPL. The most frequent postsynaptic targets of nNOS-labeled amacrine cells were other amacrine cell processes in strata 1 to 3 of the IPL. Conclusion:These studies show that nNOS-immunoreactive neurons of the macaque monkey retina constitute a subpopulation of GABAergic neurons as in the other mammals examined, and suggest that nNOS-containing amacrine neurons may influence inner retinal circuitry, thus mediating visual processing.

Keywords: 557 retina: proximal(bipolar, amacrine, and ganglion cells) • 556 retina: neurochemistry • 491 nitric oxide