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Results for “Retinal Horizontal Cells”

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PubMed2006

GABAergic circuitry in the opossum retina: a GABA release induced by L-aspartate.

Glutamate and gamma-amino butyric acid (GABA) are the major excitatory and inhibitory neurotransmitters, respectively, in the central nervous system (CNS), including the retina. Although in a number of studies the retinal source of GABA was identified, in several species, as horizontal, amacrine cells and cells in the ganglion cell layer, nothing was described for the opossum retina. Thus, the first goal of this study was to determine the pattern of GABAergic cell expression in the South America opossum retina by using an immunohistochemical approach for GABA and for its synthetic enzyme, glutamic acid decarboxylase (GAD). GABA and GAD immunoreactivity showed a similar cellular pattern by appearing in a few faint horizontal cells, topic and displaced amacrine cells. In an effort to extend the knowledge of the opossum retinal circuitry, the possible influence of glutamatergic inputs in GABAergic cells was also studied. Retinas were stimulated with different glutamatergic agonists and aspartate (Asp), and the GABA remaining in the tissue was detected by immunohistochemical procedures. The exposure of retinas to NMDA and kainate resulted the reduction of the number of GABA immunoreactive topic and displaced amacrine cells. The Asp treatment also resulted in reduction of the number of GABA immunoreactive amacrine cells but, in contrast, the displaced amacrine cells were not affected. Finally, the Asp effect was totally blocked by MK-801. This result suggests that Asp could be indeed a putative neurotransmitter in this non-placental animal by acting on an amacrine cell sub-population of GABA-positive NMDA-sensitive cells.

Amacrine Cells↗

PubMed2005

Inner and outer retinal pathways both contribute to surround inhibition of salamander ganglion cells.

Illumination of the receptive-field surround reduces the sensitivity of a retinal ganglion cell to centre illumination. The steady, antagonistic receptive-field surround of retinal ganglion cells is classically attributed to the signalling of horizontal cells in the outer plexiform layer (OPL). However, amacrine cell signalling in the inner plexiform layer (IPL) also contributes to the steady receptive-field surround of the ganglion cell. We examined the contributions of these two forms of presynaptic lateral inhibition to ganglion cell light sensitivity by measuring the effects of surround illumination on EPSCs evoked by centre illumination. GABA(C) receptor antagonists reduced inhibition attributed to dim surround illumination, suggesting that this inhibition was mediated by signalling to bipolar cell axon terminals. Brighter surround illumination further reduced the light sensitivity of the ganglion cell. The bright surround effects on the EPSCs were insensitive to GABA receptor blockers. Perturbing outer retinal signalling with either carbenoxolone or cobalt blocked the effects of the bright surround illumination, but not the effects of dim surround illumination. We found that the light sensitivities of presynaptic, inhibitory pathways in the IPL and OPL were different. GABA(C) receptor blockers reduced dim surround inhibition, suggesting it was mediated in the IPL. By contrast, carbenoxolone and cobalt reduced bright surround, suggesting it was mediated by horizontal cells in the OPL. Direct amacrine cell input to ganglion cells, mediated by GABA(A) receptors, comprised another surround pathway that was most effectively activated by bright illumination. Our results suggest that surround activation of lateral pathways in the IPL and OPL differently modulate the sensitivity of the ganglion cell to centre illumination.

Animals↗

PubMed1995

Radial and tangential dispersion patterns in the mouse retina are cell-class specific.

The retina is derived from a pseudostratified germinal zone in which the relative position of a progenitor cell is believed to determine the position of the progeny aligned in the radial axis. Such a developmental mechanism would ensure that radial arrays of cells which comprise functional units in the mature central nervous system are also clonally related. The present study has tested this hypothesis by using X chromosome-inactivation transgenic mosaic mice. We report that the retina shows a conspicuous distinction for clonally related neuroblasts of different laminar and functional fates: the rod photoreceptor, Müller, and bipolar cells are aligned in the radial axis, whereas the cone photoreceptor, horizontal, amacrine, and ganglion cells are tangentially displaced with respect to them. These results indicate that the dispersion of cell classes across the retinal surface is differentially constrained. Some classes of retinal neuroblast exhibit a significant tangential, as well as radial, component in their dispersion from the germinal zone, whereas others disperse only in the radial dimension. Consequently, the majority of radial columns within the mature retina must be derived from multiple progenitors. Because the cone photoreceptor, horizontal, amacrine, and ganglion cells establish nonrandom matrices in their cellular distributions within the respective retinal layers, tangential dispersion may be the means by which these matrices are constructed.

Animals↗

PubMed2002

Spike-dependent GABA inputs to bipolar cell axon terminals contribute to lateral inhibition of retinal ganglion cells.

The inhibitory surround signal in retinal ganglion cells is usually attributed to lateral horizontal cell signaling in the outer plexiform layer (OPL). However, recent evidence suggests that lateral inhibition at the inner plexiform layer (IPL) also contributes to the ganglion cell receptive field surround. Although amacrine cell input to ganglion cells mediates a component of this lateral inhibition, it is not known if presynaptic inhibition to bipolar cell terminals also contributes to surround signaling. We investigated the role of presynaptic inhibition by recording from bipolar cells in the salamander retinal slice. TTX reduced light-evoked GABAergic inhibitory postsynaptic currents (IPSCs) in bipolar cells, indicating that presynaptic pathways mediate lateral inhibition in the IPL. Photoreceptor and bipolar cell synaptic transmission were unaffected by TTX, indicating that its main effect was in the IPL. To rule out indirect actions of TTX, we bypassed lateral signaling in the outer retina by either electrically stimulating bipolar cells or by puffing kainate (KA) directly onto amacrine cell processes lateral to the recorded cell. In bipolar and ganglion cells, TTX suppressed laterally evoked IPSCs, demonstrating that both pre- and postsynaptic lateral signaling in the IPL depended on action potentials. By contrast, locally evoked IPSCs in both cell types were only weakly suppressed by TTX, indicating that local inhibition was not as dependent on action potentials. Our results show a TTX-sensitive lateral inhibitory input to bipolar cell terminals, which acts in concert with direct lateral inhibition to give rise to the GABAergic surround in ganglion cells.

Action Potentials↗

PubMed1999

Primate retina: cell types, circuits and color opponency.

The link between morphology and physiology for some of the cell types of the macaque monkey retina is reviewed with emphasis on understanding the neural mechanism for spectral opponency in the light response of ganglion cells. An in vitro preparation of the retina is used in which morphologically identified cell types are selectively targeted for intracellular recording and staining under microscopic control. The goal is to trace the physiological signals from the long (L), middle (M) and short-wavelength sensitive (S) cones to identified cell types that participate in opponent and non-opponent signal pathways. Heterochromatic modulation photometry and silent substitution are used to characterize L-, M- or S-cone inputs to the receptive fields of distinct horizontal cell, bipolar cell, ganglion cell and amacrine cell types. The majority of the retinal cell types await detailed analysis, and knowledge of the mechanisms of opponency remains incomplete. However results thus far have established: (1) Horizontal cell interneurons make preferential connections with the three cone types, but cannot provide a basis for spectral opponency in the circuitry of the outer retina. (2) A morphologically distinctive bistratified ganglion cell type transmits a blue-ON yellow-OFF spectral opponent signal to the parvocellular division of lateral geniculate nucleus. The morphology of this ganglion cell type suggests a simple synaptic mechanism for blue yellow opponency via converging input from an S-cone connecting ON-bipolar cell and an L - M cone connecting OFF-bipolar cell. (3) Midget ganglion cells, whose axons project to the parvocellular layers of the lateral geniculate nucleus and are assumed to be the origin of red/green opponent signals, show a non-opponent, achromatic physiology when recorded in the retinal periphery the underlying circuitry for red green opponency thus remains controversial, and (4) recent recordings from identified bipolar and amacrine cells in macaque suggest that a more complete accounting of opponent circuitry is a realistic goal.

Animals↗

PubMed2005

A developmental switch in the expression of aquaporin-4 and Kir4.1 from horizontal to Müller cells in mouse retina.

PURPOSE: In adult retina, aquaporin-4 (AQP4) and inwardly rectifying K(+) (Kir4.1) channels localize to astrocyte and Müller cell membranes facing vascular and vitreous compartments, optimizing clearance of extracellular K(+) and water from the synaptic layers. However, it is unknown whether these channels are expressed at early developmental stages, before gliogenesis or angiogenesis take place in the neural retina. This study was conducted to determine the presence of AQP4 and Kir4.1 proteins in the developing mouse retina. METHODS: Simultaneous AQP4 and Kir4.1 immunodetection was performed in postnatal mice 1, 9, 15, and 30 days of age. Confocal microscopy was used to identify the cellular distribution of AQP4 and Kir4.1 proteins, as well as their coexpression with the cell-selective immunomarkers Prox-1, calbindin, and neurofilament. RESULTS: AQP4 and Kir4.1 proteins were coexpressed in calbindin- and Prox1-expressing retinal neurons at birth. These neurons were identified as horizontal cells based on their position and morphology. By P15, when vision starts, AQP4 and Kir4.1 localization coordinately switched from horizontal cells to Müller glial cells. CONCLUSIONS: The findings showed that AQP4 and Kir4.1 protein expression is confined to differentiating horizontal cells before its expression in Müller cells. The finding of AQP4 in neurons is novel, since AQP4 expression within the central nervous system is restricted to glia. Also, the results demonstrated that AQP4 is a horizontal cell-specific immunomarker in neonatal retina. The transitory coexpression of AQP4 and Kir4.1 proteins by differentiating horizontal interneurons suggests that these cells mediate K(+) and water transcellular uptake until the initiation of phototransduction, when glial cells assume these functions.

Animals↗

PubMed1993

Molecular cloning of the murine JAK1 protein tyrosine kinase and its expression in the mouse central nervous system.

Degenerate oligonucleotide primers were employed in PCRs to clone protein tyrosine kinases that may play potential roles in the development of the mammalian CNS. Using one PCR clone to screen a mouse eye cDNA library, a full-length cDNA of a cytoplasmic tyrosine kinase, the homolog of human JAK1, was obtained. The murine JAK1 kinase belongs to a new family of cytoplasmic kinases that contain two tandem catalytic domains. Northern analyses indicated that murine JAK1 mRNA is expressed in a variety of tissues and cell lines. In the adult mouse eye, in situ hybridization and immunohistochemistry showed that JAK1 mRNA and protein were expressed in the retinal ganglion cell layer and the inner part of the inner nuclear layer, presumably in amacrine cells. JAK1 protein was also detected in horizontal cells and in the two synaptic layers of the adult retina. During retinal development, JAK1 protein was first detected in retinal ganglion cells and in their axons as early as embryonic day 14. Expression of JAK1 protein in amacrine cells and horizontal cells occurred only postnatally. This pattern of expression was also observed in the chick retina, suggesting an evolutionarily conserved function of JAK1 kinase in vertebrate retinal development and/or function. Immunohistochemical staining against JAK1 was detected in two areas of the adult mouse brain, the olfactory bulb and a group of cells in the hypothalamus. Together, these expression studies suggest a role for JAK1 kinase in the differentiation or function of a subset of CNS neurons.

Aging↗

PubMed2006

Evidence for a columnar organization of cones, Müller cells, and neurons in the retina of a cichlid fish.

In the retina of many lower vertebrates, the arrangement of cells, in particular of cone photoreceptors, is highly regular. The data presented in this report show that in the retina of a cichlid fish (Astatotilapia burtoni) the regular arrangement is not restricted to cone photoreceptors and their synaptic terminals but can be found in elements of the inner retina as well. A variety of immunocytochemical and other markers was used in combination with confocal microscopy on whole-mount preparations and tangential sections. Nearest neighbor analysis was performed and density recovery profiles as auto- and cross-correlograms were generated. Cells displaying a regular arrangement of their synaptic processes in matching radial register to each other were identified for each major retinal neuronal cell type except ganglion cells (i.e. photoreceptors, horizontal cells, bipolar cells, and amacrine cells). The precise location of some of the corresponding cell bodies was not as regular but still non-random, however there was no spatial cross-correlation between cell bodies of different types. The radial processes of Müller glial cells displayed a distribution correlating to the arrangement of photoreceptors and neurons. Thus, for one Müller glial cell I found two PKC-positive cone bipolar cells, a spatially corresponding grid of parvalbumin-positive amacrine cell processes, one H1 horizontal cell, and two pairs of double cones. There was no evidence among ganglion cells matching this pattern, possibly due to the lack of suitable markers. Although many other cell types do not follow this matching regular mosaic arrangement, a basic columnar building block can be postulated for the retina at least in cichlid fish. This suggests a functional radial unit from photoreceptors to the inner plexiform layer.

Animals↗

PubMed1989

Retinal ganglion cell distribution in the cebus monkey: a comparison with the cortical magnification factors.

The distribution of ganglion cells was determined in whole-mounted Cebus monkey retinae. Ganglion cell density along the horizontal meridian was asymmetric, being 1.2-4.3 higher in the nasal retinal region when compared to temporal retina at the same eccentricities. The total number of ganglion cells varied from 1.34 to 1.4 million. Ganglion cell density peaked at 49,000/mm2 about 0.5 mm nasal to the fovea. Comparison between ganglion cell density and areal cortical magnification factors for V1 and V2 reveals that the relative representation of the fovea increases in the visual cortex. This effect seems to be a general feature of the visual system of primates.

Animals↗

PubMed1998

Comparative morphology of distal neurons in larval and adult zebrafish retinas.

Distal retinal cells from larval (7-10 days postfertilization) and adult zebrafish retinas were cultured in 70% L-15 medium for 4-5 d and comparable cell types identified. Four photoreceptor types were observed in adult retinal cultures, whereas only single cones were isolated from larval retinas. Horizontal cells in both larval and adult cultures were distinguished by their large size and stellate morphology and two subtypes, A and B, were recognized. Bipolar cells were readily identified in adult cultures, but rare in larval cultures. Two bipolar cell types, large and small, were distinguished. Measurements of the various cell types are provided.

Animals↗

PubMed1996

Neurons in the cat pretectum that project to the dorsal lateral geniculate nucleus are activated during saccades.

1. Neurons in the pretectal nuclear complex that project to the ipsilateral dorsal lateral geniculate nucleus (LGNd) were identified by antidromic activation after electrical LGNd stimulation in awake cats, and their response properties were characterized to retinal image shifts elicited either by external visual stimulus movements or during spontaneous saccadic eye movements on a stationary visual stimulus, and to saccades in darkness. Eye position was monitored with the use of a scleral search coil and care was taken to assure stability of the eyes during presentation of moving visual stimuli. 2. Of a total sample of 134 cells recorded, 27 neurons were antidromically activated by electrical LGNd stimulation. In addition, responses from neurons that were not activated from the LGNd were also analyzed, including 19 "retinal slip" cells, which selectively respond to slow horizontal stimulus movements, and 21 "jerk" cells, which are specifically activated by rapid stimulus shifts. All recorded neurons were located in the nucleus of the optic tract and in the posterior pretectal nucleus. 3. In the light, neurons identified as projecting to the LGNd responded maximally to saccadic eye movements and to externally generated sudden shifts of large visual stimuli. Slow stimulus drifts did not activate these neurons. Response latencies were shorter and peak activities were increased during saccades compared with pure visual stimulation. No systematic correlation between response latency, response duration, or the number of spikes in the response and saccade direction, saccade amplitude, or saccade duration was found. Saccades and rapid stimulus shifts in the light also activated jerk cells but not retinal slip cells. 4. All 27 antidromically activated neurons also responded to spontaneous saccadic eye movements in complete darkness. Responses to saccades in the dark, however, had longer response latencies and lower peak activities than responses to saccades in light. As in the light, response parameters in darkness seemed not to code specific saccade parameters. Cells that were not activated from LGNd were found to be unresponsive to saccades in the dark. 5. According to their specific activation by saccades in darkness, LGNd-projecting pretectal neurons are termed "saccade neurons" to distinguish them from other pretectal cell populations, in particular from jerk neurons, which show similar response properties in light. 6. The saccade-related activation of pretectal saccade neurons may be used to modulate visual responses of LGNd relay cells following saccadic eye movements. Because the pretectogeniculate projection in cat most likely is GABAergic and terminates on inhibitory LGNd interneurons, its activation may lead to a saccade-locked disinhibition of relay cells. This input could counter the strong inhibition induced in the LGNd after shifts of gaze direction and lead to a resetting of LGNd cell activity.

Animals↗

PubMed1998

Chondroitin sulfate proteoglycan specific to retinal horizontal neurons.

ABSTRACT Proteoglycans (PGs) are a diverse group of highly glycosylated macromolecules that are implicated in the development and maintenance of neuronal circuitry. With its highly ordered, layered structure, the retina ideally serves to define the synthesis, processing, and distribution of these molecules within a specific cellular subpopulation. In retinal sections, monoclonal antibody (MAb) 6A2 immunostained a horizontal cell-specific antigen. Antigen 6A2 was expressed within abundant processes in the outer plexiform layer and in rare neurites that extend across the inner nuclear layer to the inner plexiform layer. Ultrastructurally, the antigen was localized to cisternae within horizontal cell somata, along tubulovesicular structures in dendrites, and in the perisynaptic space encircling presynaptic terminals of the cone photoreceptor triad. These findings suggest that this PG is synthesized within the horizontal cells, transported to the terminals, and released into the extracellular spaces just proximal to the synapse. Based on the focal stain in the adjacent photoreceptor cell, it is possible that antigen is pinocytosed by this cell and is concentrated at the ribbon synapse. In Western immunoblots of retinal homogenates, MAb 6A2 recognized a heterogeneous chondroitin sulfate (CS) PG (CSPG) of approximately 400-500 kDa. After sequential enzymatic removal of CS glycosaminoglycans, a major broad band of 300-500 kDa was identified by MAb 1B5, which detects CSPGs that bear uronic acid linked to unsulfated N-acetylgalactosamine as the initial disaccharide in the CS chain. Localization of this PG around presynaptic terminals of the horizontal neuron and at the ribbon synapse suggests that it may play a modulatory and sustaining role at the synapse.

Animals↗

PubMed1977

Sequential differentiation of retinal cells in the mouse studied by diaphorase staining.

During retinal development in mice the early stages of differentiating of ganglion, amacrine and horizontal cells are characterized by high diaphorase activity in the perikarya. The reaction in the ganglion cells, which start differentiation at day 12 of gestation when the layer of nerve fibres is developing, was first localized near the axonal end, but later, in the period of dendritic growth, it shifted to the scleral side. Amacrine cells were first detected on day 16, and showed a transient activity at the initial stage of their differentiation. A variety of large amacrine cells with long bifurcating processes appeared at day 7 after birth, and showed particularly high TPN diaphorase activity. The horizontal cells could be followed from the 16th day of embryonic life. Their activity increased during the period of formation of the outer plexiform layer. Along the outer limiting membrane diaphorase activity was marked from day 13 of embryonic life, and seemed to concentrate later in the rod inner segments. Activity in the bipolar cells first appeared at day 7 after birth, and increased therafter, coinciding with the period of synaptic development in the outer, plexiform layer. Activity in the Müller cells appeared around 14 days after birth, and was most pronounced in the inner processes and basal end feet. The sequential differentiation of retinal cells and cellular interrelationships during retinal histogenesis are discussed.

Animals↗

PubMed1999

Retinoic acid modulates gap junctional permeability between horizontal cells of the mammalian retina.

In the retina, all-trans retinoic acid (at-RA) could function as a light signal because its production increases with the level of illumination. Given the well-established effects of retinoic acid on cell coupling in other tissues, it is possible that the changing levels of at-RA modulate the gap junctional permeability between retinal neurons. This study examines the effects of retinoic acid on horizontal cell coupling, which is known to be modulated by the ambient light level. Single horizontal cells were injected under visual control with either Neurobiotin (mouse retina) or Lucifer yellow (rabbit retina) and the extent of tracer coupling or dye coupling was used to monitor the gap junctional permeability. In the mouse retina, the injection of Neurobiotin revealed a network of approximately 150-250 tracer-coupled horizontal cells. The tracer coupling was completely abolished by incubating the retina in 150 microM at-RA for 35 min. In the rabbit retina, the injection of Lucifer yellow into A-type horizontal cells revealed networks of approximately 15-30 dye-coupled horizontal cells. Incubation in 150 microM at-RA reduced the dye coupling within 12 min and complete uncoupling was achieved after 35 min. The uncoupling effects of at-RA in the mouse and rabbit retinas were concentration- and time-dependent and they were reversible after washout. The coupling was not affected by either the 9-cis form of retinoic acid or by at-RA that had been isomerized by intensive light. The uncoupling effect of at-RA persisted following treatment with a D1 receptor antagonist and thus was dopamine-independent. This study has established that at-RA is able to modulate the gap junctional permeability between horizontal cells in the mammalian retina, where its light-dependent release has already been demonstrated.

Animals↗

PubMed1999

Retinal structure and visual acuity in a polyprotodont marsupial, the fat-tailed dunnart (Sminthopsis crassicaudata).

The visual system of the fat-tailed dunnart (Sminthopsis crassicaudata), a small polyprotodont marsupial, has been examined both anatomically and behaviourally. The ganglion cell layer was examined in cresyl-violet stained wholemounts and found to contain a mean of 81,400 ganglion cells (SD +/- 3,360); the identification of ganglion cells was supported by a correspondence to optic axon counts. Ganglion cells were distributed as a mid-temporally situated area centralis, embedded in a pronounced visual streak. Localised implants of horseradish peroxidase into retinal wholemounts revealed both A-type and B-type horizontal cells. Sections of the outer retina showed it to be rod-dominated, with a rod-to-cone ratio of 40:1 at the area centralis; cones were found to contain oil droplets but double cones were not a prominent feature. The retinal pigment epithelium consisted of squamous cells. Visual acuity, estimated from counts of peak ganglion cell density (8,300/mm2, SD +/- 1,180) and measurements of posterior nodal distance (2.9 mm), was found to be 2.30 cycles per degree. The value was close to that of 2.36 cycles per degree estimated by behavioural tests using a Mitchell jumping stand; values were similar at low, intermediate and high light levels. Our findings are discussed in relation to the lifestyle of the dunnart.

Animals↗

PubMed1979

Effects of catecholamines and related compounds on horizontal cells in the fish retina.

The effects of catecholamines (CA) and certain related compounds in the superfusate were examined on the intracellularly recorded potential from horizontal cells in the fish (Eugerres plumieri) retina. The stimulated retinal area consisted of a central spot 1.0 mm in diameter and an annulus 2.0 mm in inner diameter and 4.0 mm in outer diameter; both forms of monochromatic stimuli were centered relative to the recording microelectrode. Each of the CA (dopamine, noradrenaline, and adrenaline) produced an analogous effect on the hyperpolarizing response of all types of horizontal cells. The depolarizing response of the C (R/G)-type cells was found to change variably with the CA. The effect of dopamine (DA) among the CA was most pronounced when they were used at an equivalent amount. With 10--50 microM, the action of DA was variable but in general its effect was to increase slightly both center and surround responses. In some cases, however, DA initially augmented the surround and reduced the center response. Large amounts of the CA (100--200 microM) augmented the center response and attenuated the surround response considerably; these reciprocal changes usually were associated with moderate depolarization of the cells (5--10 mV). Recovery then occurred in 15--20 minutes. These results indicate that the CA, up to a certain amount, do not directly affect the transmission from photoreceptors to horizontal cells, since the center response became larger. At the same time, the lateral propagation of an S-potential appears to be selectively affected by the CA, suggesting that the adrenergic system participates in this phenomenon. When an excess of these compounds (200-500 microM) was given, the cells were rapidly depolarized to near 0 MV and eventually the light-induced responses were abolished. Large amounts (5--10 mM) of metabolic products of the CA (DOPAC and VMA) were found to reduce the center response slightly more than the surround. alpha-Methylnoradrenaline, 5-hydroxydopamine, and serotonin also caused the same but less effect on horizontal cells as did DA. Reserpine and clonidine mimicked the CA effect only if these compounds had been preceded by repeated applications of one of the CA or if the retina had been pretreated with Marplan. Propranolol, haloperidol, and apomorphine affected neither the horizontal cell membrane potential nor the CA effect. However, phentolamine in large amounts (500 microM) markedly diminished the DA action. Therefore, alpha-adrenergic receptors appear to be involved in the CA-induced changes observed in the horizontal cell response.

3,4-Dihydroxyphenylacetic Acid↗

PubMed2007

Distribution of soluble guanylyl cyclase in rat retina.

The nitric oxide (NO)-cGMP pathway is implicated in modulation of visual information processing in the retina. Despite numerous functional studies of this pathway, information about the retinal distribution of the major downstream effector of NO, soluble guanylyl cyclase (sGC), is very limited. In the present work, we have used immunohistochemistry and multiple labeling to determine the distribution of sGC in rat retina. sGC was present at high levels in inner retina but barely detectable in outer retina. Photoreceptors and horizontal cells, as well as Müller cells, were immunonegative, whereas retinal ganglion cells exhibited moderate staining for sGC. Strong immunostaining was found in subpopulations of bipolar and amacrine cells, but staining was weak in rod bipolar cells, and AII amacrine cells were immunonegative. Double labeling of sGC with neuronal nitric oxide synthase showed that the two proteins are generally located in adjacent puncta in inner plexiform layer, implying paracrine interactions. Our results suggest that the NO-cGMP pathway modulates the neural circuitry in inner retina, preferentially within the cone pathway.

Animals↗

PubMed1987

Responses of Purkinje cells and mossy fibres in the flocculus of the monkey during sinusoidal movements of a visual pattern.

1. Discharges of Purkinje cells (P cells) and mossy fibres were recorded from the cerebellar flocculus of monkeys trained to fixate a stationary visual target. The units were tested with a sinusoidally moving random dot pattern (background) which was projected on an entire screen or on part of it. The receptive field organization of the units was tested by changing the area of stimulus presentation on the screen and by changing the direction of visual fixation. 2. When stimulated with sinusoidal movements of the background in the horizontal plane, ninety-two of 684 Purkinje cells (13.5%) responded to the retinal-slip velocity. Seventy-eight of the ninety-two visually responsive Purkinje cells (84.8%) also showed cyclic modulations in activity during horizontal smooth-pursuit eye movements (these were so-called horizontal gaze-velocity Purkinje cells). 3. In response to the sinusoidal retinal-slip velocity, the visual Purkinje cells showed six types of discharge patterns. Type 1 Purkinje cells (28/92 or 30.4%) were directionally selective: they showed a peak activity during background movement in one direction and a trough in the other. Both peaks and troughs were related to stimulus velocities. Their receptive fields were relatively large (greater than 45 deg) and included the fovea. 4. Type 2 (8/92 or 8.7%) and type 3 (5/92 or 5.4%) Purkinje cells showed sinusoidal responses similar to those of type 1 Purkinje cells, but the visual inputs were primarily excitatory in type 2 Purkinje cells and inhibitory in type 3 Purkinje cells. Only the peaks in type 2 and troughs in type 3 were related to stimulus velocities. 5. Type 4 (4/92 or 4.3%) and type 5 (11/92 or 12.0%) Purkinje cells showed responses to stimulus movements in both directions (bidirectional). When the moving background was projected with 10 deg of fixation, type 4 Purkinje cells were excited bidirectionally in relation to retinal-slip velocities. When the periphery of either hemiretina was stimulated, type 5 Purkinje cells were inhibited and the trough activity was stimulus-velocity dependent. Receptive fields were found in the ipsilateral hemiretinae in seven type 5 Purkinje cells and in the contralateral hemiretinae in the remaining four type 5 Purkinje cells. 6. Type 6 (36/92 or 39.1% Purkinje cells received an excitatory input from the central retina and an inhibitory input from the periphery. The peripheral receptive fields were either in the ipsilateral (69.4%) or contralateral (30.6%) hemiretinae of both eyes.(ABSTRACT TRUNCATED AT 400 WORDS)

Action Potentials↗