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Results for “Retinal Horizontal Cells”

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PubMed1981

A quantitative analysis of the direction-specific response of Neurons in the cat's nucleus of the optic tract.

All cells in the nucleus of the optic tract (NOT) of the cat, that could be activated antidromically from the inferior olive, were shown to be direction-specific, as influenced by horizontal movements of an extensive visual stimulus. Cells in the left NOT were activated by leftward and inhibited by rightward movement, while those in the right NOT were activated by rightward and inhibited by leftward movement. Vertical movements did not modulate the spontaneous activity of the cells. The mean spontaneous discharge rate in 50 NOT cells was 30 spikes/s. This direction-specific response was maintained over a broad velocity range (Less Than 0.1 degrees - Greater Than 100 degrees/s). Velocities over 200 degrees/s could inhibit NOT cells regardless of stimulus direction. All cells in the NOT were driven by the contralateral eye, about half of them by the ipsilateral eye also. In addition, activation through the contralateral eye was stronger in most binocular units. Binocular cells preferred the same direction in the visual space through both eyes. An area approximately corresponding to the visual streak in the cat's retina projected most densely onto NOT cells. This included an extensive ipsilateral projection. No clear retinotopic order was seen. The most sensitive zone in the very large receptive fields (most diameters being Greater Than 20 degrees) was along the horizontal zero meridian of the visual field. The retinal input to NOT cells was mediated by W-fibers. The striking similarities between the input characteristics of NOT-cells and optokinetic nystagmus are discussed. The direction selectivity and ocular dominance of the NOT system as a whole can provide a possible explanation for the directional asymmetry in the cat's optokinetic nystagmus when only one eye is stimulated.

Animals↗

PubMed1992

GABA-like immunoreactive neurons in the retina of Bufo marinus: evidence for the presence of GABA-containing ganglion cells.

gamma-Aminobutyric acid (GABA)-like immunoreactive (IR) neurons in the retina of the cane toad Bufo marinus were revealed using immunohistochemistry on retinal wholemount preparation and sectioned material. GABA-IR neurons included horizontal, bipolar and amacrine cells in the inner nuclear layer and small to medium sized cells in the ganglion cell layer. A few IR axons were seen in the optic fiber layer of the retina. Following the injection of the carbocyanine dye, DiI into the optic tectum ganglion cells were retrogradely filled. A small population of DiI-filled ganglion cells (2.8%) was found to be GABA-IR. GABA-IR neurons in the ganglion cell layer without DiI label were considered to be displaced amacrine cells of which 45.3% were GABA positive. It is proposed that GABA-containing ganglion cells may form an inhibitory projection to visual centers of the anuran brain.

Animals↗

PubMed1988

Dynamics of skate horizontal cells.

The all-rod retina of the skate (Raja erinacea or R. oscellata) is known to have the remarkable capability of responding to incremental flashes superimposed on background intensities that initially block all light-evoked responses and are well above the level at which rods saturate in mixed rod/cone retinas. To examine further the unusual properties of the skate visual system, we have analyzed responses of their horizontal cells to intensity-modulated step, sinusoidal, and white-noise stimuli. We found that during exposures to mean intensities bright enough to block responses to incremental stimuli, decremental stimuli were also initially blocked. Thereafter, the horizontal cells underwent a slow recovery phase during which there was marked nonlinearity in their response properties. The cell first (within 2-3 min) responded to decrements in intensity and later (after greater than 10 min) became responsive to incremental stimuli. After adaptation to a steady state, however, the responses to intensity modulation were nearly linear over a broad range of modulation depths even at the brightest mean levels of illumination. Indeed, examination of the steady-state responses over a 5-log-unit range of mean intensities revealed that the amplitude of the white noise-evoked responses depended solely on contrast, and was independent of the retinal irradiance as the latter was increased from 0.02 to 20 muW/cm2; i.e., contrast sensitivity remained unchanged over this 1,000-fold increase in mean irradiance. A decrement from the mean as brief as 2 s, however, disturbed the steady state. Another unexpected finding in this all-rod retina concerns surround-enhancement, a phenomenon observed previously for cone-mediated responses of horizontal cells in the retinas of turtle and catfish. While exposure to annular illumination induced response compression and a pronounced sensitivity loss in response to incremental light flashes delivered to the dark central region, the cell's sensitivity showed a significant increase when tested with a white noise or sinusoidally modulated central spot. Unlike horizontal cells in other retinas studied thus far, however, response dynamics remained unchanged. Responses evoked either by a small spot (0.25-mm diam) or by a large field light covering the entire retina were almost identical in time course. This is in contrast with past findings from cone-driven horizontal cells whose response waveform (dynamics) was dependent upon the size of the retinal area stimulated.

Animals↗

PubMed1986

The responsiveness of Clare-Bishop neurons to motion cues for motion stereopsis.

Under paralysis of eye movement and optical adjustment of visual axes of the two eyes, neuronal responsiveness in cat Clare-Bishop (CB) cortex to the binocular presentation of visual stimuli was studied using two types of visual stimulator which presented: 3-dimensional motion of a visual stimulus; and the motion cues (movement of retinal images in the two eyes) contained in the 3-dimensional motion. On the basis of the responsiveness to 3-dimensional motion presented by the first type of stimulator, the CB cells were classified into approaching (AP) cells which were selectively responsive to the approaching motion of a visual stimulus, recessive (RC) cells responsive to the recessive motion, frontoparallel (FP) cells responsive to the frontoparallel motion and non-selective (NS) cells responsive to more than two types of motion. The investigation of the CB cells with 2-dimensional motion stimulus demonstrated 3 different types of binocular interaction: facilitatory (52/239); antagonistic (33/239) or linear summation (154/239). Cells exhibiting the facilitatory interaction (n = 52) were all FP cells, those exhibiting the antagonistic interaction were either AP (n = 25) or RC cells (n = 8), and those exhibiting the linear summation were comprised of all varieties of cells (49 AP, 17 RC, 31 FP and 57 NS cells). The cells responsive to the approaching (37 AP cells) or recessive motion between the center of the receptive area and the nose (10 RC cells), or frontoparallel motion (42 FP cells) in the horizontal direction exhibited the selective responsiveness to the motion disparity (a combination of horizontal movement of retinal images in the two eyes), and those responsive to the vertically or obliquely deviating approaching (20 AP cells) or recessive motion (14 RC cells), or frontoparallel motion in the vertical or oblique directions (13 FP cells) exhibited that for a combination of the motion disparity and the frontoparallel motion in the vertical or oblique direction. These findings indicate that the CB cell responsiveness to 3-dimensional motion of a visual stimulus is explained by the binocular integration of motion signal viewed by each eye.

Action Potentials↗

PubMed1998

Differential regulation of ciliary neurotrophic factor receptor-alpha expression in all major neuronal cell classes during development of the chick retina.

Ciliary neurotrophic factor (CNTF) exerts a multiplicity of effects on a broad spectrum of target cells, including retinal neurons. To investigate how this functional complexity relates to the regulation of CNTF receptor alpha (CNTFR alpha) expression, we have studied the developmental expression of the receptor protein in chick retina by using immunocytochemistry. During the course of development, the receptor is expressed in all retinal layers, but three levels of specificity can be observed. First, the expression is regulated temporally with immunoreactivity observed in ganglion cells (embryonic day 8 [E8] to adult), photoreceptor precursors (E8-E12), amacrine cells (E10 to adult), bipolar cells (E12-E18), differentiated rods (E18 to adult), and horizontal cells (adult). Second, expression is restricted to distinct subpopulations of principal retinal neurons: preferentially, large ganglion cells; subpopulations of amacrine cells, including a particular type of cholinergic neuron; a distinctly located type of bipolar cell; and rod photoreceptors. Third, expression exhibits subcellular restriction: it is confined largely to dendrites in mature amacrine cells and is restricted entirely to outer segments in mature rods. These data correlate with CNTF effects on the survival of ganglion cells and mature photoreceptors, the in vitro differentiation of photoreceptor precursors and cholinergic amacrine cells, and the number of bipolar cells in culture described here or in previous studies. Thus, our results demonstrate an exceptional degree of complexity with respect to the regulation of neuronal CNTFR alpha expression in a defined model system. This suggests that the same signaling pathway is used to mediate a variety of regulatory influences, depending on the developmental stage and cell type.

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PubMed1990

The developing visual system and metamorphosis in the lamprey.

Metamorphosis of the sea lamprey, Petromyzon marinus, is a true metamorphosis. The larval lamprey is a filter-feeder who dwells in the silt of freshwater streams and the adult is an active predator found in large lakes or the sea. The transformation usually occurs in the fifth or sixth year of life. Enlargement of the eye has been long accepted as a distinctive indication of metamorphosis in the sea lamprey, but it had been thought that this was because eye development in the larva was arrested after the formation of only the small central region. Recent studies indicate that all of the retina begins its development in the larva and that ganglion, amacrine, and horizontal cells differentiate in the peripheral retina of the larva. Retinal development is arrested during the premetamorphic period, to be resumed during metamorphosis. Metamorphic contributions include the differentiation of photoreceptor and bipolar cells. With the early appearance of ganglion cells, retinal pathways to the thalamus and tectum are established in larvae, as is a centripetal pathway. Tectal development spans the larval period but a spurt in tectal growth and differentiation is correlated with the completion of the retinal circuitry late in metamorphosis. The metamorphic changes in retina and tectum complete the functional development of the visual system and provide for the adult lamprey's predatory and reproductive behavior.

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PubMed1987

The distribution of F-actin in cells isolated from vertebrate retinas.

Filamentous actin has been localized in isolated retinal neurons and glia using fluorescent phallotoxin. Photoreceptors, bipolar cells, horizontal cells, amacrine cells and Müller (glial) cells were isolated by gentle enzymatic digestion of frog, lizard, rabbit, rat and cat retinas. The cells were then fixed in paraformaldehyde and stained with rhodamine-phalloidin. The patterns of fluorescence recorded were specific for each cell type. All interneurons had spots of bright fluorescence along dendrites and (or) axon terminals, probably corresponding to synaptic sites. Horizontal cells and Müller cells had a continuous subplasmalemmal layer of fluorescence throughout; this layer was also present in bipolar cells, but only in the region of cytoplasm at the base of the dendrites. Müller cells also had bright fluorescence in their apical microvilli and terminal web and associated with the zonulae adhaerentes junctions between Müller cells and photoreceptors. All photoreceptors exhibited fluorescence in their synaptic terminals, in a ring just sclerad to the nucleus (corresponding to zonulae adhaerentes junctions formed with Müller cells), and in cables running longitudinally in the inner segment. Frog photoreceptors also had processes alongside their outer segments. Rods from mammals and Xenopus had distinct spots of fluorescence at the outer segment base in a region that suggests involvement with morphogenesis of new outer-segment disc membrane.

Actins↗

PubMed1987

Relationships between ganglion cell dendritic structure and retinal topography in the cat.

The morphology of ganglion cell dendritic trees varies across the cat retina. Evidence is presented that the variation in two attributes of ganglion cell dendritic structure can be accounted for by specific aspects of the topography of the adult and developing retina. The first attribute considered was the displacement of the center of the dendritic field from the cell body in the plane of the retina. The results of this study provide evidence that most ganglion cell dendritic fields are displaced away from neighboring cells, i.e., down the retinal ganglion cell density gradient. Because of the systematic dendritic displacement locally, the centers of the dendritic fields are arranged in a more precise mosaic than are their cell bodies. The second attribute considered was the elongation and orientation of the dendritic fields. From approximately embryonic day 50 to postnatal day 10 the cat retina undergoes a process of maturation (reviewed by Rapaport and Stone: Neuroscience 11:289-301, '84) that begins at the area centralis and spreads over the retina in a horizontally elongated wave. We found that the elongation and orientation of retinal ganglion cell dendritic fields is significantly correlated with the shape of the wave of maturation. The orientation of a dendritic field is not predicted by the direction of its displacement nor is it directly related to the distribution of neighboring retinal ganglion cells. These results indicate that the displacement of a ganglion cell's dendritic field from its cell body results from mechanisms different from those responsible for the orientation of the dendritic field. Factors that may be responsible for these two attributes of ganglion cell dendritic morphology are discussed.

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PubMedDate not supplied

Sub-millimolar cobalt selectively inhibits the receptive field surround of retinal neurons.

Recent work has indicated that cobalt, at sub-millimolar concentrations, blocks horizontal cell (HC) to cone feedback, without attenuating direct cone to second-order cell synaptic transmission. We utilized low concentrations (0.25-0.5 mM) of cobalt to test the contribution of the feedback circuit, and other possible cobalt-sensitive mechanisms, to the receptive-field surrounds of retinal neurons. In the great majority of cases, low cobalt blocked ganglion cell surrounds, and it invariably blocked driving the ganglion cell by extrinsic current injected into the HC network. Although low cobalt reduced the integrating area of the HC network, dopamine, which similarly constricted the HC receptive area, did not block ganglion cell surrounds. Low cobalt reduced a late depolarizing wave in the HC light-evoked waveform and selectively suppressed the depolarizing component of chromatic HCs, both signs of HC to cone feedback. Low cobalt also reduced or blocked completely the receptive-field surrounds of a small sample of bipolar and amacrine cells. These results implicate the HC to cone feedback synapse in the formation of the receptive-field surround of retinal neurons.

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PubMed2004

Morphological characterization of the retina of the CNGA3(-/-)Rho(-/-) mutant mouse lacking functional cones and rods.

PURPOSE: To assess the structural changes in the retina caused by a functional blockade of rods and cones and to document the time course of their degeneration. METHODS: Double knockout mice were generated by cross-breeding CNGA3(-/-) mice with Rho(-/-) mice. Retinas of mutant and wild-type mice from 3 weeks up to 12 months of age were studied by confocal light and electron microscopy. The retinas were immunostained with cell-type-specific markers and with antibodies against synapse-associated proteins and transmitter receptors. RESULTS: In 3-week-old CNGA3(-/-)Rho(-/-) mice, retinal layers showed normal structural organization, and photoreceptors established normal synaptic contacts. Until postnatal week (Pw)7, presynaptic markers and postsynaptic glutamate receptors were well expressed at the photoreceptor terminals. Photoreceptor degeneration started at Pw4, progressing to an almost complete loss by 3 months. Rod spherules showed an increase in the number of synaptic ribbons and postsynaptic elements during this early stage of degeneration, and horizontal cell processes grew into the outer nuclear layer. At later stages of retinal degeneration, the inner plexiform layer (IPL) was also affected. Rod bipolar cell axon terminals showed morphologic alterations, but the stratification pattern of cone bipolar cell axons and amacrine cell processes appeared unaffected. Transmitter receptors (GlyRalpha3, GABA(A) alpha2, GluR2/3) showed no obvious changes in the distribution and density of their synaptic clusters throughout the IPL at postnatal month 12. CONCLUSIONS: The normal structural and synaptic organization of the mutant retina at Pw3 suggests that photoreceptor light responses are not essential for the development of the retinal circuitry. However, functional photoreceptors are necessary for the maintenance of rods and cones and their contacts in the OPL, because they degenerate almost completely by 3 months after birth. Degenerative changes can also be observed in the IPL; however, they appear to have a slower time course and by 12 months of age the IPL circuitry appears to be surprisingly intact.

Animals↗

PubMed1968

Receptive fields and functional architecture of monkey striate cortex.

1. The striate cortex was studied in lightly anaesthetized macaque and spider monkeys by recording extracellularly from single units and stimulating the retinas with spots or patterns of light. Most cells can be categorized as simple, complex, or hypercomplex, with response properties very similar to those previously described in the cat. On the average, however, receptive fields are smaller, and there is a greater sensitivity to changes in stimulus orientation. A small proportion of the cells are colour coded.2. Evidence is presented for at least two independent systems of columns extending vertically from surface to white matter. Columns of the first type contain cells with common receptive-field orientations. They are similar to the orientation columns described in the cat, but are probably smaller in cross-sectional area. In the second system cells are aggregated into columns according to eye preference. The ocular dominance columns are larger than the orientation columns, and the two sets of boundaries seem to be independent.3. There is a tendency for cells to be grouped according to symmetry of responses to movement; in some regions the cells respond equally well to the two opposite directions of movement of a line, but other regions contain a mixture of cells favouring one direction and cells favouring the other.4. A horizontal organization corresponding to the cortical layering can also be discerned. The upper layers (II and the upper two-thirds of III) contain complex and hypercomplex cells, but simple cells are virtually absent. The cells are mostly binocularly driven. Simple cells are found deep in layer III, and in IV A and IV B. In layer IV B they form a large proportion of the population, whereas complex cells are rare. In layers IV A and IV B one finds units lacking orientation specificity; it is not clear whether these are cell bodies or axons of geniculate cells. In layer IV most cells are driven by one eye only; this layer consists of a mosaic with cells of some regions responding to one eye only, those of other regions responding to the other eye. Layers V and VI contain mostly complex and hypercomplex cells, binocularly driven.5. The cortex is seen as a system organized vertically and horizontally in entirely different ways. In the vertical system (in which cells lying along a vertical line in the cortex have common features) stimulus dimensions such as retinal position, line orientation, ocular dominance, and perhaps directionality of movement, are mapped in sets of superimposed but independent mosaics. The horizontal system segregates cells in layers by hierarchical orders, the lowest orders (simple cells monocularly driven) located in and near layer IV, the higher orders in the upper and lower layers.

Animals↗

PubMed2006

Neurensin-1 expression in the mouse retina during postnatal development and in the cultured retinal neurons.

Neurensin-1/Neuro-p24 (previously named Neuro-p24) is a neuron-specific membrane protein that is localized particularly in neurites. Neurensin-1 is considered to play an essential role in neurite extension during nervous development, regeneration and plasticity. To understand what role Neurensin-1 plays in retinal differentiation, we examined Neurensin-1 distribution and gene expression pattern in the postnatally developing retina of the mouse, because the retina is an excellent model for nervous development. In the postnatal day (PD) 1 retina, intense Neurensin-1 immunoreactivity was found in the optic nerve fiber layer. Faint staining was seen in the ganglion cells, presumptive amacrine and horizontal cells. As the postnatal development proceeded, the optic fibers became more intensely stained in addition to other parts of the retina such as the ganglion cells, inner plexiform layer and horizontal cells. In PD 10 retinas, the horizontal cell processes showed a prominently stained configuration. As the retina developed further to attain maturity, the staining in the retina became less pronounced, although the optic nerves remained positively stained. The distribution of Neurensin-1 mRNA was consistent with these results and confirmed that the ganglion, amacrine and horizontal cells actively synthesize Neurensin-1 in the developing retina. In the retinal cell culture from newborn mice, two types of neural cells were stained for Neurensin-1, one of which showed long processes and appeared presumptive ganglion cells. These results suggest that Neurensin-1 plays a role in the fiber extension of the retinal neurons, as has been observed in other central nervous tissues, and indicate that the developing retina is a suitable experimental model for the analysis of Neurensin function, both in vivo and in vitro.

Animals↗

PubMed2002

Association of the AMPA receptor-related postsynaptic density proteins GRIP and ABP with subsets of glutamate-sensitive neurons in the rat retina.

We used specific antibodies against two postsynaptic density proteins, GRIP (glutamate receptor interacting protein) and ABP (AMPA receptor-binding protein), to study their distribution in the rat retina. In the central nervous system, it has been shown that both proteins bind strongly to the AMPA glutamate receptor (GluR) 2/3 subunits, but not other GluRs, through a set of three PDZ domains. Western blots detected a single GRIP protein that was virtually identical in retina and brain, whereas retinal ABP corresponded to only one of three ABP peptides found in brain. The retinal distributions of GluR2/3, GRIP, and ABP immunoreactivity (IR) were similar but not identical. GluR2/3 immunoreactivity (IR) was abundant in both plexiform layers and in large perikarya. ABP IR was concentrated in large perikarya but was sparse in the plexiform layers, whereas GRIP IR was relatively more abundant in the plexiform layers than in perikarya. Immunolabel for these three antibodies consisted of puncta < or = 0.2 microm in diameter. The cellular localization of GRIP and ABP IR was examined by double labeling subclasses of retinal neuron with characteristic marker proteins, e.g., calbindin. GRIP, ABP, and GluR2/3 IR were detected in horizontal cells, dopaminergic and glycinergic AII amacrine cells and large ganglion cells. Immunolabel was absent in rod bipolar and weak or absent in cholinergic amacrine cells. By using the tyramide method of signal amplification, a colocalization of GluR2/3 was found with either GRIP or ABP in horizontal cell terminals, and perikarya of amacrine and ganglion cells. Our results show that ABP and GRIP colocalize with GluR2/3 in particular subsets of retinal neuron, as was previously established for certain neurons in the brain.

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PubMed1998

Modulation of cell responses to horizontal disparities by ocular vergence in the visual cortex of the awake Macaca mulatta monkey.

Horizontal retinal disparity is the most important cue for stereopsis. However, accurate stereoscopic perception requires additional information on fixation distance. The ocular vergence angle may provide information on fixation distance and therefore may be used to calibrate horizontal disparities. We studied the responses of cells from cortical visual area V1 of one macaca mulatta monkey to dynamic random dot stereograms at different ocular vergence angles. We observed that in about half of cells sensitive to horizontal disparity the vergence angle modifies the cell responses to horizontal disparities. These results suggest that vergence angle may be used to calibrate horizontal disparities for fixation distance.

Animals↗

PubMed1992

Retinal growth and cell addition during embryogenesis in the teleost, Haplochromis burtoni.

Neurogenesis of the developing embryonic retina is described for the African cichlid fish, Haplochromis burtoni, from 4 days post fertilization until all cell phenotypes are generated (day 7). Cell addition and differentiation both begin at the same absolute location which later becomes the central retina. As observed in most other vertebrates, cones and ganglion cells differentiate first, followed by amacrine and bipolar cells. Rod photoreceptors, which are added late, differentiate last. Changes in retinal thickness, retinal stretching, cell size, and cell density were measured during development. From day 4 through 7, there is an increase in retinal thickness largely due to the expansion of the inner plexiform layer (IPL) and outer nuclear layer (ONL). The inner nuclear layer (INL) decreases in thickness and there is a transient decrease in the density of cells in the scleral portion of the INL. Cells increase in size in the ganglion cell layer (GCL) and the vitread INL, decrease in size in the sclerad INL, and remain the same in the ONL. Changes in the density of the cell layers were observed: the density of ONL cells increased, the density of GCL cells decreased, and INL cells increased then decreased. From day 4 to day 6, eye growth is entirely due to cell addition because no retinal stretching was observed in the ONL or the horizontal layer. During this same developmental period, the pattern and rate of neurogenesis were measured in the differentiated portion of the retina by means of 3H-thymidine labeling. A small number of cell divisions within the differentiated INL precede the onset of cell divisions in the ONL. The number of 3H-thymidine labeled cells within the INL increases at a low rate consistent with an asymmetric pattern of cell division characteristic of stem cells. In contrast, cell divisions in the ONL increase exponentially, consistent with a symmetric pattern of cell division characteristic of progenitor cells. Double-label experiments (3H-thymidine and a rod specific opsin antibody) show that some of the symmetrically dividing cells in the ONL express the rod specific opsin within 2 days, suggesting that these dividing cells are rod progenitors. Although we do not hae conclusive evidence, these developmental processes support the hypothesis that stem cells within the INL could be the source of rod precursors in the embryonic teleost retina.

Animals↗

PubMed1990

Retinal ganglion cell distribution and behaviour in procellariiform seabirds.

Retinal ganglion cell distribution in nine species of procellariiform seabirds was studied by Nissl staining of retinal whole-mounts and the construction of density contour maps. Most species showed a horizontal linear area of high cell density, but concentric distributions with dorsal and central cell concentrations were found in two species. These results are discussed in relation to the birds' foraging behaviour.

Animals↗

PubMedDate not supplied

Mapping photoreceptor and postreceptoral labelling patterns using a channel permeable probe (agmatine) during development in the normal and RCS rat retina.

The aim of this study was to determine whether agmatine, a channel permeable probe, can identify photoreceptor dysfunction in the Royal College of Surgeons (RCS) retina at an earlier stage to that shown by apoptosis or anatomical markers, and also characterize the neurochemical development of the inner retina in the normal and degenerating rat. We used isolated retinas at different ages incubated in physiological media containing agmatine. Subsequently, postembedding immunocytochemistry was used to determine the number of labelled photoreceptors and the labelling pattern within postreceptoral neurons. Agmatine labelling patterns revealed a sequential development of retinal neurons beginning at postnatal day (PND) 11/12 with most horizontal cells, a few ganglion and amacrine cells, showing a strong signal. The neurochemical development progressed rapidly, and reflects to a large part the known distribution of glutamate receptors, with inner nuclear labelling being evident by PND14, continuing with the same pattern of labelling in adulthood for the control retina. The RCS retina showed markedly reduced agmatine labelling in the inner retina at PND20. A rapid increase in photoreceptor AGB labelling was evident during the degeneration phase. Multiple samples at PND14 and PND16 confirmed a significant increase of labelled photoreceptors in the RCS retina.

Agmatine↗

PubMed1989

Distribution of muscarinic acetylcholine receptors on processes of isolated retinal cells.

Binding of propylbenzilylcholine mustard, a muscarinic acetylcholine receptor antagonist, to isolated retinal cells was examined with light microscopic autoradiography. Dissociation of the adult tiger salamander retina yielded identifiable rod, cone, horizontal, bipolar, amacrine/ganglion, and Müller cells. Preservation of fine structure was assessed with conventional electron microscopy. For all cell types, the plasmalemma was intact and free of adhering debris; in addition, presynaptic ribbon complexes were present in photoreceptor and bipolar axon terminals indicating that synaptic structures were retained. Specific binding to cell bodies and processes was analyzed separately by using morphometric and statistical techniques. The highest grain densities occurred on processes of amacrine/ganglion cells and axons and 2 degrees and 3 degrees dendrites of bipolar neurons. Bipolar cells, however, seemed to be a heterogeneous population because there was great variation in the density of binding sites on both their axons and distal dendrites. Intermediate levels of binding were found on bipolar 1 degree dendrites and horizontal cells. No specific binding was detected on Müller cells and most parts of photoreceptors. Comparisons between cells showed that grain densities were similar for bipolar axons and amacrine/ganglion cell processes but bipolar dendrites were richer in binding sites than horizontal cell dendrites. Thus, muscarinic receptors in the salamander retina are located on amacrine/ganglion, bipolar, and horizontal cells and primarily confined to the processes which compose the two synaptic layers. In the inner plexiform layer, muscarinic receptors reside on processes from all three inner retinal neurons: in the outer synaptic layer, receptors are only on second-order cells and are more numerous along bipolar than horizontal cell dendrites.

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