Biplexiform ganglion cells contact photoreceptors in the retina of the greenling Hexagrammos octogrammus

Abstract

The biplexiform cell (bpxRGC) is a relatively and recently discovered type of retinal ganglion cells. Like "ordinary" ganglion cells, bpxRGCs have dendrites arborizing within the inner plexiform layer. However, as distinct from other ganglion cells, they have dendrites ascending to the outer plexiform layer. To date, bpxRGCs have been found in mammals, amphibians, and teleost fishes (Cook et al. [1996] Vis Neurosci 13:517-528). The mammalian and amphibian bpxRGCs form direct contacts with photoreceptors and may participate in rapid signal transmission to the brain (Mariani [1982] Science 216:1134-1136; Straznicky and Gábriel [1995] J Hirnforsch 36:135-141). The synaptic organization of teleost bpxRGCs has not been studied. We have studied the synaptic structure of bpxRGCs in the teleost fish Hexagrammos octogrammus. In the sclerad part of the outer plexiform layer, bpxRGC dendrites occurred among the elements in invaginated ribbon synapses (triads) in cone pedicles and rod spherules. Earlier, we showed that greenling bpxRGCs project to the optic tectum (Podugolnikova et al. [2002] Sensornye systemy 15:44-53). We suggest that greenling bpxRGCs participate in some of the tectum-mediated reactions requiring a quick launch of visuomotor reflexes.

Melanopsin ganglion cells extend dendrites into the outer retina during early postnatal development

“…The only prior description of a biplexiform ganglion cell in mammals was based on observations in macaques (Mariani, ; Zrenner et al, ), but others have provided compelling evidence for reinterpreting that type as horizontal cells that have been displaced to the inner retina, perhaps through errors in retinal development (Wassle et al, ). In teleosts, a distinctive biplexiform ganglion cell has been described, with confirmed axon in the optic nerve, and dual dendritic arbors, one in the outermost layer of the IPL and a second in the OPL (Cook et al, ; Pushchin and Kalachev, ), a pattern strikingly similar to that of immature melanopsin ganglion cells with ORDs. Direct contacts between photoreceptors and ganglion‐cell dendrites are the rule rather than the exception in the hagfish, a jawless vertebrate whose primitive retinas apparently lack horizontal, bipolar and amacrine cells (Holmberg, ; Lamb et al, ).…”

Classification of retinal ganglion cells in the southern hemisphere lamprey Geotria australis (Cyclostomata)

“…Biplexiform retinal ganglion cells in gnathostomes are thought to participate in a tectum‐mediated reflex for rapid visual‐motor responses (Pushchin and Kalachev, ). The dendrites projecting to the outer layers of the retina of these biplexiform retinal ganglion cells have been observed to contact photoreceptors directly in both gnathostomes (Mariani, ; Pushchin and Kalachev, ) and lampreys (De Miguel et al, ; Rio et al, ), suggesting that these cells provide a direct link from photoreceptors to retinal ganglion cells, which may aid in rapid reflex functions.…”

Structure and diversity of retinal ganglion cells in steller's sculpin Myoxocephalus stelleri tilesius, 1811

“…Dimming detectors would be the closest candidates. However, both in fish and other vertebrates, biplexiform cells, along with conventional synapses within the IPL, form direct synapses with photoreceptors (Mariani, ; Straznicky and Gábriel, ; Pushchin and Kalachev, ). Therefore, their RF properties probably differ from those of dimming detectors.…”

“…form direct synapses with photoreceptors (Mariani, 1982;Straznicky and G abriel, 1995;Pushchin and Kalachev, 2010). Therefore, their RF properties probably differ from those of dimming detectors.…”