Localization of nitric oxide synthase in the tree shrew retina

Abstract

Nitric oxide (NO) is a novel neuronal messenger that likely influences retinal function by activating retinal guanylyl cyclase to increase levels of cGMP. In the present study, the localization of neuronal nitric oxide synthase (nNOS, Type I NOS) in the cone-dominant tree shrew retina was studied using NADPH-d histochemistry and nNOS immunocytochemistry. Both NADPH-d and nNOS-immunoreactivity (IR) labeled the inner segments of rods and the myoids of a regular subpopulation of cones, with their corresponding nuclei outlined. The labeled cone myoids were co-localized with a marker for short-wave-sensitive (SWS) cones (S-antigen) and also displayed the regular triangular packing and density (7%) characteristic of SWS cones in tree shrew and other mammalian retinas. These measures confirmed the identity of the labeled cones as SWS cones. Photoreceptor ellipsoids of all cones were strongly labeled by NADPH-d reactivity, but lacked nNOS-IR. Another novel finding in tree shrew retina was that both NADPH-d and nNOS-IR labeled Muller cells, which have not been labeled by nNOS-IR in other mammalian retinas. Consistent with findings in rod-dominant retinas, two types of amacrine cells at the vitreal edge of the inner nuclear layer and a subpopulation of displaced amacrine cells at the scleral edge of the ganglion cell layer were labeled by both NADPH-d and nNOS-IR. Processes of these labeled cells were seen to extend into the inner plexiform layer, where dense punctate label was seen, especially in the central sublamina. These results show that localization of NOS in the cone-dominant tree shrew retina shares some common properties with rod-dominant mammalian retinas, but also shows some species-specific characteristics. The new finding of nNOS localization in tree shrew SWS cones and rods, but not in other cones, raises interesting questions about the roles of NO in the earliest level of visual processing.

Neuronal nitric oxide synthase immunoreactive neurons in the mammalian retina

“…Furthermore, by using immunocytochemistry and NADPH-d histochemistry to study the cone-dominated retina of the tree shrew, it has been possible to reveal several patterns of activity in the cellular subcompartments of the spectral classes of cones, in particular in short wavelength cones (SWS). This finding suggests that NO may be differentially involved in the activity of different classes of photoreceptors (Petry and Murphy, 1995;Cao et al, 1999). …”

Relationship of the Optical Coherence Tomography Signal to Underlying Retinal Histology in the Tree Shrew (Tupaia belangeri)

“…Studies in chick 28 and swine 29 retinas support the present results, as the inner plexiform-inner nuclear layer histologic boundary is usually proximal to the LRP boundary T3a. The alignment of T3a with the border between amacrine and Müller cell somas may be explained by the known properties of Müller cell somas, which are more polygonal than either amacrine or bipolar cell somas [61][62][63] and so may alter the backscattering properties of the retina. In addition, the Müller cell density in tree shrew retina has been found to be similar to primate in central retina (both greater than 20,000 cells per mm 2 ), 63,64 so that Müller cells form a close-knit sublayer within the inner nuclear layer (Fig.…”

“…1 MathWorks). Ten sublaminae boundaries were identified in the histologic sections by using established anatomic criteria45,50,61,62 (Figs. 2, 3A)…”

Physiological assessment of high glucose neurotoxicity in mouse and rat retinal explants

“…Organotypic retinal explants have been used for multiple studies of retinal function and pathologies. Among their advantages in the investigation of retinal diseases is the possibility to fully control biochemical parameters and to study direct neurodegenerative processes independent from vascular system function (Caffe et al, ; Cao, Murphy, & Petry, ; Li, Zhang, Qi, & Su, ; Müller, Wagner, Lorenz, & Stieger, ; Paquet‐Durand, Hauck, Van Veen, Ueffing, & Ekström, ). For example, retinal explant cultures from healthy rats and mice have been used to simulate diabetic conditions by adding or removing glucose and insulin from the composition of the culture medium (Matteucci et al, ; Valdés et al, ).…”