Morphology and synaptic connectivity of nitric oxide synthase-immunoreactive neurons in the guinea pig retina

Abstract

Immunocytochemical methods with an antiserum against neuronal nitric oxide synthase (NOS) were applied to identify the morphology and synaptic connectivity of NOS-like immunoreactive neurons in the guinea pig retina. In the present study, two types of amacrine cells were labeled with anti-NOS antisera. Type 1 cells had large somata located in the inner nuclear layer (INL) with long, sparsely branched processes ramifying mainly in stratum 3 of the inner plexiform layer (IPL). The somata of type 2 cells (smaller diameters) were located in the INL. Some displaced amacrine cells in the ganglion cell layer were labeled. The soma size of the displaced amacrine cells was similar to that of the type 2 amacrine cells. However, processes originating from type 2 amacrine cells and displaced amacrine cells stratified mainly in strata 1 and 5, respectively. Some cone bipolar cells were weakly NOS-immunoreactive. The synaptic connectivity of NOS-like immunoreactive amacrine cells was identified in the IPL by electron microscopy. NOS-labeled amacrine cell processes received synaptic input from other amacrine cell processes and bipolar cell axon terminals in all strata of the IPL. The most frequent postsynaptic targets of NOS-immunoreactive amacrine cells were other amacrine cell processes. Cone bipolar cells were postsynaptic to NOS-labeled amacrine cells in all strata of the IPL. Labeled amacrine cells synapsing onto ganglion cells were found only in sublamina b. A few synaptic contacts were observed between labeled cell processes. In the outer plexiform layer, dendrites of labeled bipolar cells made basal contact with cone pedicles or formed a synaptic triad opposed to a synaptic ribbon of cone pedicles.

Light responses and morphology of bNOS‐immunoreactive neurons in the mouse retina

“…αGCs have been reported to couple with both αGCs and ACs (Pang et al 2003; Hidaka et al, 2004; Schubert et al, 2005). Beside gap junctions, NOACs also make chemical synapses onto other ACs and GCs (Oh et al 1999). These chemical synapses are expected to be GABAergic (Kim IB, et al, 1999) and nitric oxidergic; but how the NO release is modulated by presynaptic events is mostly unknown.…”

“…Based on the ultrastructure of the somas and staining intensity, NOACs were generally classified into two major types in earlier reports (Oh et al, 1999; Kim et al, 2000), namely type I and type II. The type I cells have large extensively stained somas, while type II cells posses small and weakly stained somas.…”

“…light) or pathological signals. The morphology of NOACs has been studied in some detail in the retinas of turtles (Haverkamp et al, 2000; Eldred and Blute, 2005), rats (Chun et al, 1999), and guinea pigs (Oh et al, 1999), but the identity of some NOS immunoreactive cells is not clear (Haverkamp et al, 2000). Due to the breakthrough in the discovery of mouse genome and the development of many transgenic mouse strains, the mouse model has become the most promising animal model in biological and medical research.…”

Neuronal nitric oxide synthase immunoreactive neurons in the mammalian retina

“…Immunoreactivity for nNOS in the guinea pig retina has been reported in detail by Oh et al (1999). They found that nNOS-labeled cells were distributed sparsely throughout the retina.…”

“…This assumption has been corroborated by the fact that NADPH-d is colocalized with NOS in several neuronal systems Perez et al, 1995) and also by the fact that an NADPH-d reaction is not detected in the retinae of mice devoid of the neuronal NOS gene (Darius et al, 1995). Thus, NADPH-d histochemistry (Sandell, 1985;Sagar, 1986Sagar, , 1990Mü ller et al, 1988;Cobcroft et al, 1989;Mitrofanis, 1989;Osborne et al, 1993;Lau et al, 1994) and immunocytochemical methods using anti-NOS antisera Koistinaho et al, 1993;Yamamoto et al, 1993;Oh et al, 1998Oh et al, , 1999Chun et al, 1999;Kim et al, 1999) have been applied to study the morphology and topographical distribution of NOS cells in the mammalian retina.…”