Biomaterial Database

The neuronal organization of the outer plexiform layer of the primate retina. 1984

A P Mariani

In the primate retina at the level of the first synapse in the visual system, the outer plexiform layer, processes from 15 different types of neurons have so far been described. These are the synaptic spherules of rods, the pedicles of three spectral types of cones, dendrites and axons of two types of horizontal cell, dendrites of seven types of bipolar cell, processes of interplexiform cells, and the outwardly coursing dendritic extensions of biplexiform ganglion cells. The interconnections of these neurons as studied by electron microscopy and Golgi-EM are presented in a summary diagram (Fig. 27). Basal processes from cone pedicles contact the cone pedicles, and rod spherules forming gap junctions. The dendrites of both types of horizontal cell (hI and hII) connect only to cone pedicles and form lateral elements of triads at the ribbon synaptic complex. The HI axon terminals end as lateral elements at rod spherules while the axons of HII horizontal cells connect with cones in a manner similar to their dendrites. Interplexiform cells (ipc) do not contact either rod or cone synaptic endings. Rod bipolar cell (rb) dendrites end as central elements at the ribbon synaptic complex of rod spherules. The dendrites of flat midget (fm), flat top (fb), and giant bistratified bipolar (gb) cells all form basal junctions with cone pedicles. Ending as central elements of triads at cone pedicles are the dendrites of invaginating midget (im), diffuse invaginating cone (ib), and blue-cone (bb) bipolar cells. Biplexiform ganglion cells (bgc) connect to rods as central elements opposite the synaptic ribbon in the spherules. As compared to an earlier summary diagram of the outer plexiform layer (Kolb, 1970), the primate retina is now known not to be as simply organized as was once thought. Although our knowledge of the types of neurons contributing processes to this first synaptic layer, and the nature of their connections with other neurons has been broadened, especially within the past few years, this summary diagram is not intended to represent the complete or final "picture." Undoubtedly, future investigations along the lines of research outlined here will provide additional details to this wiring diagram so that we may better understand the processing of visual information by neurons in the retina.

UI	MeSH Term	Description	Entries
D007365	Intercellular Junctions	Direct contact of a cell with a neighboring cell. Most such junctions are too small to be resolved by light microscopy, but they can be visualized by conventional or freeze-fracture electron microscopy, both of which show that the interacting CELL MEMBRANE and often the underlying CYTOPLASM and the intervening EXTRACELLULAR SPACE are highly specialized in these regions. (From Alberts et al., Molecular Biology of the Cell, 2d ed, p792)	Cell Junctions,Cell Junction,Intercellular Junction,Junction, Cell,Junction, Intercellular,Junctions, Cell,Junctions, Intercellular
D008854	Microscopy, Electron	Microscopy using an electron beam, instead of light, to visualize the sample, thereby allowing much greater magnification. The interactions of ELECTRONS with specimens are used to provide information about the fine structure of that specimen. In TRANSMISSION ELECTRON MICROSCOPY the reactions of the electrons that are transmitted through the specimen are imaged. In SCANNING ELECTRON MICROSCOPY an electron beam falls at a non-normal angle on the specimen and the image is derived from the reactions occurring above the plane of the specimen.	Electron Microscopy
D010786	Photoreceptor Cells	Specialized cells that detect and transduce light. They are classified into two types based on their light reception structure, the ciliary photoreceptors and the rhabdomeric photoreceptors with MICROVILLI. Ciliary photoreceptor cells use OPSINS that activate a PHOSPHODIESTERASE phosphodiesterase cascade. Rhabdomeric photoreceptor cells use opsins that activate a PHOSPHOLIPASE C cascade.	Ciliary Photoreceptor Cells,Ciliary Photoreceptors,Rhabdomeric Photoreceptor Cells,Rhabdomeric Photoreceptors,Cell, Ciliary Photoreceptor,Cell, Photoreceptor,Cell, Rhabdomeric Photoreceptor,Cells, Ciliary Photoreceptor,Cells, Photoreceptor,Cells, Rhabdomeric Photoreceptor,Ciliary Photoreceptor,Ciliary Photoreceptor Cell,Photoreceptor Cell,Photoreceptor Cell, Ciliary,Photoreceptor Cell, Rhabdomeric,Photoreceptor Cells, Ciliary,Photoreceptor Cells, Rhabdomeric,Photoreceptor, Ciliary,Photoreceptor, Rhabdomeric,Photoreceptors, Ciliary,Photoreceptors, Rhabdomeric,Rhabdomeric Photoreceptor,Rhabdomeric Photoreceptor Cell
D011323	Primates	An order of mammals consisting of more than 300 species that include LEMURS; LORISIDAE; TARSIERS; MONKEYS; and HOMINIDS. They are characterized by a relatively large brain when compared with other terrestrial mammals, forward-facing eyes, the presence of a CALCARINE SULCUS, and specialized MECHANORECEPTORS in the hands and feet which allow the perception of light touch.	Primate
D012160	Retina	The ten-layered nervous tissue membrane of the eye. It is continuous with the OPTIC NERVE and receives images of external objects and transmits visual impulses to the brain. Its outer surface is in contact with the CHOROID and the inner surface with the VITREOUS BODY. The outer-most layer is pigmented, whereas the inner nine layers are transparent.	Ora Serrata
D000818	Animals	Unicellular or multicellular, heterotrophic organisms, that have sensation and the power of voluntary movement. Under the older five kingdom paradigm, Animalia was one of the kingdoms. Under the modern three domain model, Animalia represents one of the many groups in the domain EUKARYOTA.	Animal,Metazoa,Animalia
D013569	Synapses	Specialized junctions at which a neuron communicates with a target cell. At classical synapses, a neuron's presynaptic terminal releases a chemical transmitter stored in synaptic vesicles which diffuses across a narrow synaptic cleft and activates receptors on the postsynaptic membrane of the target cell. The target may be a dendrite, cell body, or axon of another neuron, or a specialized region of a muscle or secretory cell. Neurons may also communicate via direct electrical coupling with ELECTRICAL SYNAPSES. Several other non-synaptic chemical or electric signal transmitting processes occur via extracellular mediated interactions.	Synapse