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Results for “Retinal Bipolar Cells”

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PubMed1981

Effects of concanavalin A on developing ganglion cells in the retina of chick embryos.

The administration of concanavalin A (Con A) (50-200 microgram/egg) to chick embryos between the third and the seventh day of incubation has the following effects on the retina: (1) Con A causes the degeneration of a large number of ganglion cells and consequently the layer that should be formed by these cells is not present or is constituted only by a small number of ganglion cells. (2) The lectin seems to be effective only when it is administered during the postmitotic phase of the ganglion cells. (3) The degenerated cells are phagocytosed by the Müller cells in a manner similar to that occurring during the natural cell death in normal retinal development. (4) The differentiation of other retinal elements (photoreceptors, bipolar, amacrine and Müller cells) is not affected by the lectin administration. (5) The administration of Con A in later stages of development, even at ten times higher dosages (2000 microgram/egg), fails to affect retinal neurogenesis. It is suggested that Con A binding to receptor sites of the cell membrane affects the distribution or mobility of surface components producing an alteration in the mechanism by which the developing cells regulate positional information during retinal neurogenesis.

Animals↗

PubMed1997

Reducing extracellular Cl- suppresses dihydropyridine-sensitive Ca2+ currents and synaptic transmission in amphibian photoreceptors.

A reduction in extracellular chloride suppresses light-evoked currents of second-order retinal neurons (bipolar and horizontal cells) by reducing release of glutamate from photoreceptors. The underlying mechanisms responsible for this action of reduced extracellular Cl- were studied with a combination of electrophysiological recordings from single neurons in a retinal slice preparation and image analyses of intracellular Ca2+ (Fura-2) and pH [2',7'-bis-(2-carboxyethyl)-5-(and-6)-carboxyfluorescein, acetoxymethyl ester] in dissociated photoreceptors. The results show that reducing extracellular Cl- suppresses a dihydropyridine (DHP)-sensitive Ca2+ current (I(Ca)) in photoreceptors. It is proposed that suppression of I(Ca) results in suppression of photoreceptor neurotransmission. The suppressive effect of low Cl- on I(Ca) is not due to antagonism by the substituting anion nor is it mediated by changes in extracellular or intracellular pH. We conclude that normal extracellular levels of Cl- are important for maintenance of the voltage-gated Ca2+ channels that support neurotransmission from photoreceptors. Several ideas are presented about the mechanisms by which Cl- supports photoreceptor neurotransmission and the possibility that modulations of Cl- might play a physiological role in the regulation of Ca2+ channels in photoreceptors and, hence, photoreceptor function.

Ambystoma↗

PubMed1998

Temporal contrast enhancement via GABAC feedback at bipolar terminals in the tiger salamander retina.

Most retinal amacrine (ACs) and ganglion cells (GCs) express temporal contrast by generating action potentials at only the onset and offset of the light stimulus. This study investigated the neural mechanisms that underlie this temporal contrast enhancement. Whole cell patch recordings were made from bipolar cells (BCs), ACs, and GCs in the retinal slice preparation. The cells were identified by the locations of their somas in the inner nuclear layer and ganglion cell layers, their characteristic light responses, and morphology revealed by Lucifer yellow staining. Depolarizing a single BC with a brief voltage pulse elicited a Cl- tail current that was completely abolished when Ca2+ entry to bipolar terminals was prevented, by either removing Ca2+ from the Ringer solution or blocking Ca2+ channels with Co2+. This suggests that the Cl- current is Ca2+-dependent. In those bipolar cells whose axon terminals were cutoff during slicing no Cl- current was observed, indicating that this current is generated at the synaptic terminals. The Cl- current consists of a predominant synaptic component that can be blocked by the non-N-methyl--aspartate (NMDA) glutamate receptor antagonist 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX) or by the gamma-aminobutyric acid-C (GABAC) receptor antagonist picrotoxin. There also exists a relatively small nonsynaptic component. Thus both glutamatergic and GABAergic transmission were involved in the generation of this Cl- current, suggesting that it is mediated by a recurrent feedback to bipolar cells. Picrotoxin, which blocks both GABAC receptors at BC terminals and GABAA receptors on the dendrites of ACs and GCs, converted the light-elicited voltage response in most - ACs and GCs from transient to sustained. Bicuculline, which blocks only the GABAA receptors, did not prolong the transient response in - ACs and GCs. This suggests that a negative feedback mediated by the GABAC receptor on the bipolar terminals is responsible for making these responses transient. After the GABAergic feedback was blocked with picrotoxin the light-elicited voltage responses (recorded under current clamp) were more sustained than the current responses (recorded under voltage clamp) to the same light stimuli. This suggests that a voltage-dependent conductance converts the relatively transient current responses to more sustained voltage responses. Our results imply a synaptically driven local GABAergic feedback at bipolar terminals, mediated by GABAC receptors. This feedback appears to be a significant component of the mechanism underlying temporal contrast enhancement in - ACs and GCs.

Animals↗

PubMed2000

Rate of quantal excitation to a retinal ganglion cell evoked by sensory input.

To determine the rate and statistics of light-evoked transmitter release from bipolar synapses, intracellular recordings were made from ON-alpha ganglion cells in the periphery of the intact, superfused, cat retina. Sodium channels were blocked with tetrodotoxin to prevent action potentials. A light bar covering the receptive field center excited the bipolar cells that contact the alpha cell and evoked a transient then a sustained depolarization. The sustained depolarization was quantified as change in mean voltage (Deltav), and the increase in voltage noise that accompanied it was quantified as change in voltage variance (Deltasigma(2)). As light intensity increased, Deltav and Deltasigma(2) both increased, but their ratio held constant. This behavior is consistent with Poisson arrival of transmitter quanta at the ganglion cell. The response component attributable to glutamate quanta from bipolar synapses was isolated by application of 6-cyano-7-nitroquinoxaline (CNQX). As CNQX concentration increased, the signal/noise ratio of this response component (Deltav(CNQX)/Deltasigma(CNQX)) held constant. This is also consistent with Poisson arrival and justified the application of fluctuation analysis. Two different methods of fluctuation analysis applied to Deltav(CNQX) and Deltasigma(CNQX) produced similar results, leading to an estimate that a just-maximal sustained response was caused by approximately 3,700 quanta s(-1). The transient response was caused by a rate that was no more than 10-fold greater. Because the ON-alpha cell at this retinal locus has approximately 2,200 bipolar synapses, one synapse released approximately 1.7 quanta s(-1) for the sustained response and no more than 17 quanta s(-1) for the transient. Consequently, within the ganglion cell's integration interval, here calculated to be approximately 16 ms, a bipolar synapse rarely releases more than one quantum. Thus for just-maximal sustained and transient depolarizations, the conductance modulated by a single bipolar cell synapse is limited to the quantal conductance ( approximately 100 pS at its peak). This helps preserve linear summation of quanta. The Deltav/Deltasigma(2) ratio remained constant even as the ganglion cell's response saturated, which suggested that even at the peak of sensory input, summation remains linear, and that saturation occurs before the bipolar synapse.

6-Cyano-7-nitroquinoxaline-2,3-dione↗

PubMed1988

The activities of host and graft glial cells following retinal transplantation into the lesioned adult rat eye: developmental expression of glial markers.

We have studied the time course of the expression of glial fibrillary acidic protein (GFAP) and S-100 developmentally regulated proteins in host and graft tissue after transplantation of rat E15 retina to retinal lesion sites of adult rat hosts. Host Müller cell reactivity (GFAP staining) appeared in the peripheral retina 4.5 h after the lesion apparently in response to axotomy of the retinal ganglion cells, and then spread out in a declining wave over the whole dorsoventral extent of the retina within 1 day. From 2 days after transplantation, host glial cells appeared to migrate into the graft along the open host/graft interface, graft surfaces and blood vessels (at 8 days). Intrinsic graft glial cells (mostly Müller cells) developed approximately according to a normal time-table, but became partially reactive at 3 weeks and completely reactive at 5 weeks after transplantation. However, this reactivity seemed to have no effect on the formation of retinal laminae. Bipolar graft Müller cells were found most frequently in graft rosettes, forming an external limiting membrane around receptor inner segments, but no continuous inner limiting membrane on the vitreal surface. This was probably due to the disruption of the inner limiting membrane during transplantation, the lack or scarcity of ganglion cells or the random distribution of astrocytes in the graft.

Animals↗

PubMed1993

Properties of synaptic transmission from photoreceptors to bipolar cells in the mudpuppy retina.

1. Simultaneous, whole-cell recordings were obtained from synaptically coupled photoreceptor/bipolar cell pairs, by the use of direct visualization in a superfused, mudpuppy retinal slice preparation. 2. OFF-bipolar cells (BPs) generated sign-conserving responses when extrinsic current was injected into rods and cones, whereas ON-BPs generated a sign-reversing response. OFF-BPs (n = 24) responded faster than ON-BPs (n = 12), in terms of response latency (27.8 vs. 80.6 ms) and peak response times (50.5 vs. 159.8 ms) when current was injected into photoreceptors. We did not detect any significant difference between rod- versus cone-mediated latency or peak response times in the ON- and OFF-BP subtypes. 3. Rod and cone inputs to OFF-BPs were blocked by kynurenic acid (Kyn), but the doses required were significantly higher for rod inputs: the IC50 (the concentration at which an antagonist blocks 50% of the responses) for Kyn was 0.3 mM for cone inputs and 1 mM for rod inputs. 4. Rod inputs to OFF-BPs showed the same Kyn sensitivity as rod inputs to horizontal cells (HCs). However, cone inputs to HCs (IC50 < 200 microM) were more sensitive to Kyn than those to OFF-BPs. 5. The pharmacological studies presented here, together with previous studies, suggest that the sign-conserving pathway in the outer plexiform layer of the mudpuppy retina involves at least three subtypes of glutamate receptors: 1) cone-activated receptors of HCs; 2) cone-activated receptors of OFF-BPs; and 3) rod-activated receptors found in HCs and BPs.(ABSTRACT TRUNCATED AT 250 WORDS)

Aminobutyrates↗

PubMedDate not supplied

Functional properties of a metabotropic glutamate receptor at dendritic synapses of ON bipolar cells in the amphibian retina.

Perforated patch-voltage and current-clamp recordings were obtained from ON bipolar cells in the amphibian retinal slice preparation. The currents produced by the photoreceptor transmitter were compared to the currents produced by selective metabotropic glutamate agonists: L-2-amino-4-phosphonobutyrate (L-AP4, APB) and IS,3R 1-amino-1,3 cyclopentanedicarboxylic acid (1S, 3R ACPD). Both agonists produced currents that were very similar to that produced by the photoreceptor transmitter in terms of conductance and reversal potential. The similarities suggest that the metabotropic glutamate receptors are functionally localized to the synaptic region of ON bipolar dendrites. The synaptic conductance rarely exceeded the non-synaptic conductance. The mean input resistance of ON bipolar neurons was 770 M omega in the light and 1.2 G omega in the dark. The average light-regulated synaptic conductance was 57% of the non-synaptic conductance. The L-AP4 regulated conductance averaged 77% of the non-synaptic conductance, while the 1S, 3R ACPD regulated conductance averaged 95% of the non-synaptic conductance. This balance between synaptic and non-synaptic conductance indicates that the synapse will not shunt the cell and the conductance ratio serves to maximize incremental gain at the photoreceptor to ON bipolar synapse. This conductance mechanism makes the ON bipolar cell well equipped to relay rod signals.

Aminobutyrates↗

PubMed2001

Vsx1, a rapidly evolving paired-like homeobox gene expressed in cone bipolar cells.

The paired-like homeodomain (HD) protein Chx10 is distinguished by the presence of the CVC domain, a conserved 56 amino acid sequence C-terminal to the HD. In mammals, Chx10 is essential both for the proliferation of retinal progenitor cells and for the formation or survival of retinal bipolar interneurons. We describe the cloning and characterization of a mouse Chx10 homologue, Vsx1; phylogenetic analysis suggests that Vsx1 and its putative vertebrate orthologues have evolved rapidly. Vsx1 expression in the adult is predominantly retinal. Whereas Chx10 is expressed both in retinal progenitors in the developing eye and apparently in all bipolar cells of the mature retina, Vsx1 expression is first detected in the eye at postnatal day 5, where it is restricted to cone bipolar cells.

Amino Acid Sequence↗

PubMed1991

Rod-signal interneurons in the rabbit retina: 1. Rod bipolar cells.

The cellular morphology and topographic distribution of the rod bipolar cells in the rabbit retina have been investigated by selective labelling with protein kinase C-immunohistochemistry (Negishi et al., Neurosci, Lett. 94:247-252, 1988) and by Lucifer Yellow injection of microscopically identified cells in a superfused retinal preparation. The distribution of the rod bipolar cells parallels that of their input neurons, the rod photoreceptors, in that the rod bipolars reach maximum densities of 5,000-7,000 cells/mm2 on the inferior and superior flanks of the visual streak, dropping to slightly lower densities at the peak visual streak. The centre-to-periphery density gradient of the rod bipolars is about 2.5:1, and the density ratio of rods to rod bipolars shows little variation across the retina, ranging from 43:1 in superior retina to 58:1 in inferior retina. The dendritic field area of the rod bipolar cells increases from 600 microns2 on the visual streak to 1,200 microns2 in the far-superior retina, with each point on the retina overlapped by 2.5-3.5 dendritic fields. The axonal field area of the rod bipolar cells increases from about 100 microns2 at the peak visual streak to about 250 microns2 at the retina edge, and the axonal field coverage ranges from 0.55 in the visual streak to about 0.8 in peripheral retina. Although there appear to be gaps in the local array of rod bipolar somata, these areas are covered by the axonal arbours of neighbouring rod bipolar cells.

Animals↗

PubMed2003

Rod and cone contributions to the a-wave of the electroretinogram of the macaque.

The electroretinogram (ERG) of anaesthetised dark-adapted macaque monkeys was recorded in response to ganzfeld stimulation and rod- and cone-driven receptoral and postreceptoral components were separated and modelled. The test stimuli were brief (< 4.1 ms) flashes. The cone-driven component was isolated by delivering the stimulus shortly after a rod-saturating background had been extinguished. The rod-driven component was derived by subtracting the cone-driven component from the mixed rod-cone ERG. The initial part of the leading edge of the rod-driven a-wave scaled linearly with stimulus energy when energy was sufficiently low and, for times less than about 12 ms after the stimulus, it was well described by a linear model incorporating a distributed delay and three cascaded low-pass filter elements. Addition of a simple static saturating non-linearity with a characteristic intermediate between a hyperbolic and an exponential function was sufficient to extend application of the model to most of the leading edge of the saturated responses to high energy stimuli. It was not necessary to assume involvement of any other non-linearity or that any significant low-pass filter followed the non-linear stage of the model. A negative inner-retinal component contributed to the later part of the rod-driven a-wave. After suppressing this component by blocking ionotropic glutamate receptors, the entire a-wave up to the time of the first zero-crossing scaled with stimulus energy and was well described by summing the response of the rod model with that of a model describing the leading edge of the rod-bipolar cell response. The negative inner-retinal component essentially cancelled the early part of the rod-bipolar cell component and, for stimuli of moderate energy, made it appear that the photoreceptor current was the only significant component of the leading edge of the a-wave. The leading edge of the cone-driven a-wave included a slow phase that continued up to the peak, and was reduced in amplitude either by a rod-suppressing background or by the glutamate analogue, cis-piperidine-2,3-dicarboxylic acid (PDA). Thus the slow phase represents a postreceptoral component present in addition to a fast component of the a-wave generated by the cones themselves. At high stimulus energies, it appeared less than 5 ms after the stimulus. The leading edge of the cone-driven a-wave was adequately modelled as the sum of the output of a cone photoreceptor model similar to that for rods and a postreceptoral signal obtained by a single integration of the cone output. In addition, the output of the static non-linear stage in the cone model was subject to a low-pass filter with a time constant of no more than 1 ms. In conclusion, postreceptoral components must be taken into account when interpreting the leading edge of the rod- and cone-driven a-waves of the dark-adapted ERG.

Animals↗

PubMedDate not supplied

Glycine- and GABA-activated inhibitory currents on axon terminals of rabbit cone bipolar cells.

Glycine- and GABA-activated currents were examined in the axon terminals of 12 types of rabbit cone bipolar cells. In the superfused retinal slice, a cell was voltage clamped at 0 mV in the presence of cobalt; then glycine or GABA was puffed onto the axon terminal. Types CBa1, CBa2, and a few CBa1-2 cells demonstrated larger glycine-activated currents than GABA-activated ones. However, some OFF cells (CBa2(n), CBa1-2(n), CBa1(w)), most CBa1-2, and most ON cells (CBb3, CBb3-4, CBb3(n), and CBb4) displayed larger GABA-activated currents. The ON cell, CBb5, possessed only a GABA-activated current. The predominance of glycinergic currents in CBa1, CBa2, and a few CBa1-2 cells suggests a major input from the glycinergic AII amacrine cell and thus a key role for these cells in the rod bipolar pathway. Certain OFF cells (most CBa1-2) expressed larger GABA-activated currents. All types expressed both GABA(A) and GABAC currents about equally, although most OFF types (CBa1, CB a2(n), CBa1-2, and CBa2(n)) displayed a slightly greater GABA(A) component.

Adult↗

PubMed1997

Differentiation and morphogenesis in pellet cultures of developing rat retinal cells.

We previously developed a reaggregate cell culture system (pellet cultures) in which retinal neuroepithelial cells proliferate and give rise to rod photoreceptor cells (rods) in vitro (Watanabe and Raff, 1990, Neuron 4:461-467). In the present study, we analyzed cell differentiation and morphogenesis in pellet cultures by using both cell-type-specific markers with immunofluorescence and electron microscopy. We demonstrated that, in addition to rods, the other major retinal cell types, including amacrine cells, bipolar cells, Müller cells, and ganglion cells were all present in the pellets, where most were able to develop from dividing precursor cells in vitro. The different cell types in the pellets became organized into two distinct structures: dark rosettes and pale rosettes. The cellular composition of these structures indicated that the dark rosettes correspond to the outer nuclear layer and the pale rosettes to the inner nuclear layer of the normal retina. Ultrastructural studies have indicated that the thin layer of neuronal processes surrounding the dark rosettes correspond to the outer plexiform layer, and the central region of the pale rosettes correspond to the inner plexiform layer of the normal retina. Other features of normal retinal development also occurred in the pellets, including programmed cell death and the formation of inner and outer rod cell segments and synapses. Thus, pellet cultures provide a convenient way to study different aspects of retinal development where one can control the size and the cellular composition of the initial reaggregate.

Animals↗

PubMed1980

Modelling and simulation of vertebrate retina.

In the present work we investigate the neuronal activities in a vertebrate retina by modelling and simulations using the results of (Oğuztöreli, 1979). The basic retinal network considered here consists of interconnected five neurons: a receptor cell (rod or cone), a horizontal cell, a bipolar cell, an amacrine cell, and a retinal ganglion cell. The mathematical model for the basic network is a system of nonlinear ordinary integral differential difference equations. A number of simulations describing the dynamics of the neural activities in the basic network under different conditions are presented, actual and steady-state solutions are discussed. An algorithm is proposed for the determination of the system parameters experimentally.

Animals↗

PubMed2006

Expression of the basic helix-loop-factor Olig2 in the developing retina: Olig2 as a new marker for retinal progenitors and late-born cells.

In this study, we examined the spatiotemporal expression patterns of Olig2, a basic helix-loop-helix transcription factor, in the developing mouse retina. Expression of Olig2 was initially detected on embryonic day 12.5 (E12.5). The majority of Olig2-positive cells were identified as retinal progenitor cells throughout embryogenesis. During later embryonic stages, the number of Olig2-positive retinal progenitor cells increased, and Olig2-positive cells were confined only to the neuroblast layer (NBL). Olig2 expression was not observed in the ganglion cell layer (GCL) nor in the inner nuclear layer (INL) that contain the differentiated retinal cell types, indicating that Olig2 is not expressed in differentiated cells in prenatal retina. In later postnatal stages, Olig2 expression was retained in mature neurons and glial cells, namely retinal ganglion cells (RGCs), amacrine cells (ACs), horizontal cells, bipolar cells and Müller glial cells. Thus, Olig2 is an marker both for retinal progenitor cells during embryonic stages, and also for differentiated retinal subpopulations within the GCL and INL during postnatal stages.

Animals↗

PubMed1987

Nerve fibre layer loss in diseases of the outer retinal layer.

We present examples of nerve fibre layer changes in diseases thought to affect primarily the outer retinal layers. These disease processes include cone-rod dystrophies, rod-cone dystrophies, juvenile macular degeneration (Stargardt's disease) and fundus flavimaculatis, vitelliform macular dystrophy, and Leber's congenital amaurosis. All were associated with alterations in the retinal nerve fibre layer, either diffuse or focal. The presence of these nerve fibre layer changes raises the question of transsynaptic degeneration and of possible primary or associated disease of other retinal cells than the receptors-namely, bipolar, amacrine, Mueller, or ganglion cells--in these disease of the outer retinal layer. Involvement of the nerve fibre layer also indicates the need to examine patients with defects in the nerve fibre layer by electroretinograms and other tests for outer retinal layer disease when no obvious optic nerve disease is present.

Adult↗

PubMedDate not supplied

Immunocytochemical localization of excitatory and inhibitory neurotransmitters in the zebrafish retina.

The patterns of glutamate, gamma-aminobutyric acid (GABA), and glycine distribution in the zebrafish retina were determined using immunocytochemical localization of antisera at the light-microscope level. The observed GABA immunoreactivity (GABA-IR) patterns were further characterized using antibodies to both isoforms of glutamic acid decarboxylase (GAD65 and GAD67), the synthetic enzyme for GABA. Glutamate-IR was observed in all retinal layers with photoreceptors, bipolar cells, and ganglion cells prominently labeled. Bipolar cells displayed the most intense glutamate-IR and bipolar cell axon terminals were clearly identified as puncta arranged in layers throughout the inner plexiform layer (IPL). These findings suggest the presence of multiple subtypes of presumed OFF- and ON-bipolar cells, including some ON-bipolar cells characterized by a single, large (9 microm X 6 microm) axon terminal. GABA-, GAD-, and glycine-IR were most intense in the inner retina. In general, the observed labeling patterns for GABA, GAD65, and GAD67 were similar. GABA- and GAD-IR were observed in a population of amacrine cells, a few cells in the ganglion cell layer, throughout the IPL, and in horizontal cells. In the IPL, both GABA- and GAD-IR structures were organized into two broad bands. Glycine-IR was observed in amacrine cells, interplexiform cells, and in both plexiform layers. Glycine-positive terminals were identified throughout the IPL, with a prominent band in sublamina 3 corresponding to an immunonegative region observed in sections stained for GAD and GABA. Our results show the distribution of neurons in the zebrafish retina that use glutamate, GABA, or glycine as their neurotransmitter. The observed distribution of neurotransmitters in the inner retina is consistent with previous studies of other vertebrates and suggests that the advantages of zebrafish for developmental studies may be exploited for retinal studies.

Animals↗

PubMedDate not supplied

Distribution of GABA(C)-like responses among acutely dissociated rat retinal neurons.

GABAergic responses of acutely dissociated rat retinal neurons, including both bipolar cells (BCs) and other, morphologically round cells (RCs), were assayed with the fluorescent (FL), voltage-sensitive probe oxonol DiBaC4(5). Using intensified video microscopy and simultaneous recording, GABA responses were identified in one-third of cells in a typical microscope field; of these 85% hyperpolarized (0.05-0.3 log unit FL decreases) while the remainder depolarized (0.05-0.2 log unit FL increases). GABA-sensitive cells were also TACA-sensitive (trans-4-Aminocrotonic acid), and these ligands appeared interchangeable in ability to evoke responses. In RCs, an asymmetric co-responsive pattern was observed between GABA- and muscimol-evoked events. Muscimol-sensitive RCs responded well to GABA, but not all GABA-sensitive RCs responded to muscimol. In GABA-sensitive BCs, muscimol responses were typically weak or absent. Few BCs or RCs responded to CACA (cis-4-Aminocrotonic acid). Bicuculline-resistant GABA responses occurred in approximately 80% of GABA-responsive RCs and BCs. Both bicuculline-sensitive (GABA(A)-like) and bicuculline-insensitive (GABAc-like) responses were resistant to picrotoxin. Although a small minority of GABA-sensitive cells hyperpolarized in response to R(+)baclofen, bicuculline-insensitive responses were not antagonized by 2-hydroxysaclofen, and were abolished in low [Cl-]o. Results suggested (1) that bicuculline-insensitive, Cl(-)-dependent, GABAc-like responses were broadly distributed and predominant among dissociated rat retinal neurons; (2) that muscimol was a particularly weak agonist for rat retinal BCs; and (3) that oxonol was a sensitive probe for retinal GABA responses.

Animals↗

PubMed2005

Non-image-forming ocular photoreception in vertebrates.

It has been accepted for a hundred years or more that rods and cones are the only photoreceptive cells in the retina. The light signals generated in rods and cones, after processing by downstream retinal neurons (bipolar, horizontal, amacrine and ganglion cells), are transmitted to the brain via the axons of the ganglion cells for further analysis. In the past few years, however, convincing evidence has rapidly emerged indicating that a small subset of retinal ganglion cells in mammals is also intrinsically photosensitive. Melanopsin is the signaling photopigment in these cells. The main function of the inner-retina photoreceptors is to generate and transmit non-image-forming visual information, although some role in conventional vision (image detection) is also possible.

Animals↗