Inner plexiform layer

Carotenoids accumulating in the human body are obtained exclusively from our diet. Out of almost 50 carotenoids present in a typical human diet, about 14 are absorbed into the blood (Khachik et al., 1997), and only two of them—lutein and zeaxanthin (Figure 15.1)—accumulate in the retina (Bernstein et al., 2001 Bone and Landrum, 1992 Bone et al., 1988, 1997 Davies and Morland, 2004 Khachik et al., 1997, 2002). Lutein and zeaxanthin are particularly concentrated in photoreceptor axons and inner plexiform layer in the area including and surrounding... 

Figure 14.1 Schematic diagram of the blood-retinal barrier (BRB). The retinal cell layers seen histologically consist of retinal pigment epithelium (RPE) photoreceptor outer segments (POS) outer limiting membrane (OLM) outer nuclear layer (ONL) outer plexiform layer (OPL) inner nuclear layer (INL) inner plexiform layer (IPL) ganglion cell layer (GCL) nerve fiber layer (NFL) inner limiting membrane (ILM).

Nerve fiber layer Ganglion cell layer Inner plexiform layer... 

Dopamine has been recognized to have neuroprotective actions in glaucoma. Retinal dopaminergic cells can be detected by the immunohistochemical staining of tyrosine hydroxylase, the rate-limiting enzyme in dopamine synthesis. It has been observed that NMDA induced RGC toxicity dramatically decreased tyrosine hydroxylase immunostaining at the June don betw een the inner nuclear layer and inner plexiform layer in glaucoma (Kitaoka and Kumai, 2004). 

A fully developed retina consists of six neuron types and the Muller glial cells as shown in this schematic representation. A, Amacrine cells B, bipolar cells C, cone photoreceptor cells G, ganglion cells H, horizontal cells I, interplexiform cells M, Muller cells PE, pigment epithelium R, rod photoreceptor cell INL, inner nuclear layer IPL, inner plexiform layer ONL, outer nuclear layer Ph, photoreceptors RPE, RPE (Reproduced with permission from the publishers of Sharma and Ehinger, 2003)... 

In the rat retina, mGluR5 immunoreactivity in the outer and inner plexiform layers was further observed electron-microscopically immunoreactivity in the outer plexiform layer was in dendrites of rod bipolar cells postsynaptic to rod photoreceptor terminals, while that in the inner plexiform layer was seen in amacrine cell processes postsynaptic to OFF-cone bipolar cell terminals, ON-cone bipolar cell terminals, and rod bipolar cell terminals (Koulen et al., 1997). 

In the retina of the rat, mGluR 2/3 immunoreactivity was localized exclusively in the processes of cholinergic amacrine cells, which were postsynaptic to bipolar cell synapses in the inner plexiform layer (Koulen et al., 1996). In the retina of the cat, the immunoreactivity was observed in horizontal cells and amacrine cells the immunoreactive amacrine processes were postsynaptic to cone bipolar cells and to rod bipolar terminals (Cai and Pourcho, 1999). 

In the retina of the rat, mGluR4a immunoreactivity was observed throughout the entire inner plexiform layer, exclusively at the postsynaptic targets of the cone bipolar cells and the rod bipolar cells (Koulen et al., 1996). 

GluR6 is limited to a subset of amacrine cells, while GluR7 is expressed in most amacrine and bipolar cells (inner and middle INL, respectively), but probably not in horizontal cells (IS, Brandstatter et al., 1994). KAl is not expressed in the rat retina, although described in the mouse retina (Zhang et al., 1996) in contrast, KA2 is common in cells throughout the GCL and INL (IS, Brandstatter et al., 1994). Immunolabeling for delta 1/2 is restricted to the neuropil of the inner plexiform layer (IC, Brandstatter et al., 1997). 

Species Outer segments layer Inner segments layer Outer nuclear layer Outer plexiform layer Inner nuclear layer Inner plexiform layer Ganglion cell layer Miiller cells... 

Famiglietti EV, Kolb H. A bistratilied amacrine cell and synaptic circuitry in the inner plexiform layer of the retina. Brain Res 1975 84 293-300. 

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