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PubMed1988

Glutamate and dopamine modulate synaptic plasticity in horizontal cell dendrites of fish retina.

Horizontal cell dendrites protruding into the cone pedicles in fish retina exhibit a light-dependent plasticity. In a light-adapted retina they form numerous spinules having membrane densities at their tips. These spinules disappear during dark adaptation. Experiments with light- or dark-adapted retinas which were incubated in glutamate or its agonists and antagonists, respectively, revealed that this putative cone transmitter is able to reduce the expression of spinules in a light-adapted retina. Dopamine, on the other hand, induces the formation of spinules in a dark-adapted retina and haloperidol reduces the expression in a light-adapted retina. These data suggest a control of spinules plasticity through two retinal neurotransmitter systems.

Animals↗

PubMed1997

GABAergic retinocollicular projection in the New World monkey Cebus apella.

GABA immunoreactivity was examined in the retina of the New World monkey Cebus apella. Labeled cell bodies were identified as horizontal, bipolar, interplexiform, amacrine and a population of putative ganglion cells. To determine whether ganglion cells were immunoreactive to GABA, double-labeling experiments were performed using Fast Blue as retrograde neuronal tracer injected into the superior colliculus. Retinas containing FB-labeled ganglion cells were subsequently incubated with antiserum against GABA. Although retinocollicular ganglion cells were found in three different layers (ganglion cell layer, inner nuclear layer and inner plexiform layer), our experiments revealed GABA-positive ganglion cells only in the outer half of the ganglion cell layer.

Amidines↗

PubMed2004

Microspectrophotometry of visual pigments and oil droplets in a marine bird, the wedge-tailed shearwater Puffinus pacificus: topographic variations in photoreceptor spectral characteristics.

Microspectrophotometric examination of the retina of a procellariiform marine bird, the wedge-tailed shearwater Puffinus pacificus, revealed the presence of five different types of vitamin A(1)-based visual pigment in seven different types of photoreceptor. A single class of rod contained a medium-wavelength sensitive visual pigment with a wavelength of maximum absorbance (lambda(max)) at 502 nm. Four different types of single cone contained visual pigments maximally sensitive in either the violet (VS, lambda(max) 406 nm), short (SWS, lambda(max) 450 nm), medium (MWS, lambda(max) 503 nm) or long (LWS, lambda(max) 566 nm) spectral ranges. In the peripheral retina, the SWS, MWS and LWS single cones contained pigmented oil droplets in their inner segments with cut-off wavelengths (lambda(cut)) at 445 (C-type), 506 (Y-type) and 562 nm (R-type), respectively. The VS visual pigment was paired with a transparent (T-type) oil droplet that displayed no significant absorption above at least 370 nm. Both the principal and accessory members of the double cone pair contained the same 566 nm lambda(max) visual pigment as the LWS single cones but only the principal member contained an oil droplet, which had a lambda(cut) at 413 nm. The retina had a horizontal band or 'visual streak' of increased photoreceptor density running across the retina approximately 1.5 mm dorsal to the top of the pecten. Cones in the centre of the horizontal streak were smaller and had oil droplets that were either transparent/colourless or much less pigmented than at the periphery. It is proposed that the reduction in cone oil droplet pigmentation in retinal areas associated with high visual acuity is an adaptation to compensate for the reduced photon capture ability of the narrower photoreceptors found there. Measurements of the spectral transmittance of the ocular media reveal that wavelengths down to at least 300 nm would be transmitted to the retina.

Animals↗

PubMed1990

Visual response properties and afferents of nucleus of the optic tract in the ferret.

Basic properties of responses to visual stimulation with large moving random dot patterns were studied in ferret nucleus of the optic tract. Retinal input to NOT was assessed by orthodromic electrical stimulation of the optic chiasm and optic nerves. Presence of an input from visual cortex was tested by orthodromic electrical stimulation of ipsilateral area 17. All 51 NOT neurons studied displayed a non-habituating, clearly direction-specific response: discharge rate strongly increased with the stimulus pattern moving horizontally in ipsiversive direction (motion directed towards the recorded hemisphere) and decreased with contraversive stimulus motion. Most latencies to visual stimulation ranged from 80 to 100 ms. Velocity tuning was studied using stimulus velocities between 4 deg/s and 100 deg/s. Discharge rates were most effectively modulated at a stimulus velocity of 20 deg/s. A large portion of the cells studied (91%) could be binocularly activated, although for almost all neurons the contralateral eye was dominant. Through stimulation of the optic chiasm 46 out of 51 NOT neurons could be electrically activated with a latency of 5.42 +/- 0.66 ms (mean +/- SD). For 15 fibers stimulated from both optic chiasm and contralateral optic nerve, conduction velocities between 2.5 and 8.9 m/s, with a mean of 5.1 m/s, were obtained. A major direct input from the ipsilateral retina was not found. Furthermore, 65% of all neurons could be activated through electrical stimulation of visual cortex with a mean latency of 3.7 +/- 1.5 ms, indicating a strong cortical projection to ferret NOT. The functional relevance of response properties of ferret NOT neurons for horizontal optokinetic nystagmus is discussed. Parameters that could be related to formation of a cortico-pretectal projection in mammals are considered.

Afferent Pathways↗

PubMed1994

Binocular rivalry and fusion under scotopic luminances.

A study is reported of human binocular rivalry and fusion over a range of luminances from scotopic to photopic. At scotopic light levels, rivalry alternations were very slow and complete. Suppression spread over much larger areas of the visual field than at photopic light levels. As luminances decreased from photopic to scotopic levels there was a rod-cone break for binocular rivalry. Mean suppression durations became abruptly greater as light levels dropped below those allowing the cones to be active. Horizontal disparities allowing fusion were 4 to 6 times greater at scotopic than at photopic light levels. Binocular vision at scotopic luminances was sluggish and of low resolution. It is as though connections to, and within, binocular vision are changed when light levels allow only rod input.

Adult↗

PubMed2000

Distribution of the calcium-binding proteins parvalbumin, calbindin D-28k and calretinin in the retina of two teleosts.

Using monoclonal antibodies against parvalbumin (PV) and calbindin (CB), and a polyclonal antiserum against calretinin (CR), the expression patterns of these proteins in the retina of the tench and rainbow trout were studied at light microscopic level in in toto preparations and radial sections. Parvalbumin was present in subpopulations of small amacrine cells in both species, but these cells were more abundant and had a clear centre-periphery gradient distribution in the tench. Using the McAB 300 monoclonal antibody against CB, glial cells such as Müller cells, astrocytes in the nerve fibre layer, and sparse large cells close to the entrance of the optic nerve were observed in both species. Moreover, this antibody strongly labelled H1 horizontal cells and their thick axon terminals in the tench retina, whereas only a small population of amacrine cells was stained in the trout. Calretinin was expressed in different types of ganglion cells and numerous neurones located in the inner plexiform layer in both species, but was more abundant and more strongly stained in the trout retina, where some bipolar cells were easily distinguishable. A comparison to current results in other vertebrate species is offered.

Animals↗

PubMed1996

Spatial integration and cortical dynamics.

Cells in adult primary visual cortex are capable of integrating information over much larger portions of the visual field than was originally thought. Moreover, their receptive field properties can be altered by the context within which local features are presented and by changes in visual experience. The substrate for both spatial integration and cortical plasticity is likely to be found in a plexus of long-range horizontal connections, formed by cortical pyramidal cells, which link cells within each cortical area over distances of 6-8 mm. The relationship between horizontal connections and cortical functional architecture suggests a role in visual segmentation and spatial integration. The distribution of lateral interactions within striate cortex was visualized with optical recording, and their functional consequences were explored by using comparable stimuli in human psychophysical experiments and in recordings from alert monkeys. They may represent the substrate for perceptual phenomena such as illusory contours, surface fill-in, and contour saliency. The dynamic nature of receptive field properties and cortical architecture has been seen over time scales ranging from seconds to months. One can induce a remapping of the topography of visual cortex by making focal binocular retinal lesions. Shorter-term plasticity of cortical receptive fields was observed following brief periods of visual stimulation. The mechanisms involved entailed, for the short-term changes, altering the effectiveness of existing cortical connections, and for the long-term changes, sprouting of axon collaterals and synaptogenesis. The mutability of cortical function implies a continual process of calibration and normalization of the perception of visual attributes that is dependent on sensory experience throughout adulthood and might further represent the mechanism of perceptual learning.

Animals↗

PubMedDate not supplied

Electroretinographic characteristics of proliferative vitreoretinopathy in rhegmatogenous detachment of retina.

Thirty-five patients with types A, B, C2, C3, and D1 proliferative vitreoretinopathy (PVR) were followed up for 8-14 months after surgical treatment of rhegmatogenic amotio retinae. Hanz-Feld electroretinogram (ERG), rhythmic ERG to low and high-frequency stimulation, and macular ERG were recorded. Before surgery all patients presented with specific signs of changes in the retinal electrogenesis, characteristic of rhegmatogenic amotio retinae with PVR of different types. Comparative analysis of ERG and rhythmic ERG alteration showed a more expressed reaction of Mueller's glial cells in patients with types A-C2 PVR and of second order neurons in the internal nuclear layer of the retina in those with types C3 and D1 PVR. Characteristic changes in the retinal functional activity were detected, possessing a prognostic significance. According to electrophysiological studies, the decisive factor for predicting the course of recovery after surgical treatment of retinal detachment is the preoperative function of retinal neurons. A drastic depression of low-frequency rhythmic ERG is the most unfavorable sign in prognosis of the postoperative time course of visual functions. The least favorable course of recovery after the operation is typical of amotio retinae with type C3 PVR. Recovery of amplitudes of different biopotentials and functional horizontal bonds at different levels of the retinal structure is different.

Electroretinography↗

PubMed2001

Immunocytochemical localization of kainate-selective glutamate receptor subunits GluR5, GluR6, and GluR7 in the cat retina.

Localizations of the kainate-selective glutamate receptor subunits GluR5, 6, and 7 were studied in the cat retina by light and electron microscopic immunocytochemistry. GluR5 immunoreactivity was observed in the cell bodies and dendrites of numerous cone bipolar cells and ganglion cells. The labeled cone bipolar cells make basal or flat contacts with cone pedicles in the outer plexiform layer, leading to their identification as OFF-center bipolar cells. Reaction product within the inner plexiform layer was observed in processes of ganglion cells at their sites of input from cone bipolar cells. Staining for GluR6 was localized to A- and B-type horizontal cells, numerous amacrine cells, and an occasional cone bipolar cell. The larger ganglion cells were also immunoreactive. As with other GluR molecules, labeling was usually confined to one of the two postsynaptic elements at a cone bipolar dyad contact. Immunoreactivity for GluR7 was very limited and was seen only in a few amacrine and displaced amacrine cells. Findings of this study are consistent with a major role for kainate receptors in mediating OFF pathways in the outer retina with participation in both OFF and ON pathways in the inner retina.

Animals↗

PubMed2000

The nature of surround-induced depolarizing responses in goldfish cones.

Cones in the vertebrate retina project to horizontal and bipolar cells and the horizontal cells feedback negatively to cones. This organization forms the basis for the center/surround organization of the bipolar cells, a fundamental step in the visual signal processing. Although the surround responses of bipolar cells have been recorded on many occasions, surprisingly, the underlying surround-induced responses in cones are not easily detected. In this paper, the nature of the surround-induced responses in cones is studied. Horizontal cells feed back to cones by shifting the activation function of the calcium current in cones to more negative potentials. This shift increases the calcium influx, which increases the neurotransmitter release of the cone. In this paper, we will show that under certain conditions, in addition to this increase of neurotransmitter release, a calcium-dependent chloride current will be activated, which polarizes the cone membrane potential. The question is, whether the modulation of the calcium current or the polarization of the cone membrane potential is the major determinant for feedback-mediated responses in second-order neurons. Depolarizing light responses of biphasic horizontal cells are generated by feedback from monophasic horizontal cells to cones. It was found that niflumic acid blocks the feedback-induced depolarizing responses in cones, while the shift of the calcium current activation function and the depolarizing biphasic horizontal cell responses remain intact. This shows that horizontal cells can feed back to cones, without inducing major changes in the cone membrane potential. This makes the feedback synapse from horizontal cells to cones a unique synapse. Polarization of the presynaptic (horizontal) cell leads to calcium influx in the postsynaptic cell (cone), but due to the combined activity of the calcium current and the calcium-dependent chloride current, the membrane potential of the postsynaptic cell will be hardly modulated, whereas the output of the postsynaptic cell will be strongly modulated. Since no polarization of the postsynaptic cell is needed for these feedback-mediated responses, this mechanism of synaptic transmission can modulate the neurotransmitter release in single synaptic terminals without affecting the membrane potential of the entire cell.

Animals↗

PubMed1992

GABA-mediated positive autofeedback loop controls horizontal cell kinetics in tiger salamander retina.

Horizontal cells (HCs) appear to release, and also to be sensitive to, GABA. The external GABA concentration is increased with depolarization of the HC membrane via an electrogenic GABA transporter. This extracellular GABA opens a GABAA-gated Cl- channel in the HC membrane. Since the equilibrium potential for Cl- (ECl) is near -20 mV, GABA released by the HC further depolarizes the HC. The GABA transporter and the GABAA receptor thus constitute a positive feedback loop in the HC membrane. This loop can slow down the kinetics of the light responses in HCs. GABA released via the GABA transporter can affect the GABAA receptor, probably because diffusion from the extracellular space is normally restricted by the intact retinal structure. We therefore used retinal slices rather than isolated HCs to maintain that structure. To measure single-cell currents in the slice, HCs were electrically uncoupled by including cAMP in the patch pipette. Under these conditions, bath application of GABA elicited two currents: (1) a picrotoxin-blocked current reversing near ECl, probably mediated by GABAA receptors, and (2) a picrotoxin-insensitive current similar to that elicited by cis-4-hydroxynipecotic acid (NIP) shown in other preparations to act at the GABA transporter. Under physiological conditions, the HC membrane potential is controlled by two major conductances, the GABAA-gated Cl- conductance described above, and the glutamate-gated conductance modulated by photoreceptor input. A bright light flash eliminates the glutamate-gated conductance, leaving only the GABA-gated Cl- conductance to control the membrane. With the Cl- conductance a significant fraction of the overall membrane conductance the GABAergic positive feedback loop can decrease the response kinetics. We increased the ambient extracellular GABA concentration by adding 50 microM GABA to the extracellular medium. This increased the ambient Cl- conductance, but the transporter still modulated Cl- conductance because responses to light stimuli were significantly slowed. The slowdown of the HC response could be reversed by interrupting the loop in two ways: (1) picrotoxin opened the loop and speeded the responses by uncoupling the GABA concentration from control of the membrane conductance, and (2) NIP opened the loop by uncoupling the extracellular GABA concentration from the Cl- conductance and therefore the membrane potential.(ABSTRACT TRUNCATED AT 400 WORDS)

6-Cyano-7-nitroquinoxaline-2,3-dione↗

PubMed1981

Morphology of physiologically identified W-cells in the C laminae of the cat's lateral geniculate nucleus.

The projections from the retina through the lateral geniculate nucleus to the visual cortex in the cat are comprised of three parallel, independent pathways. These three pathways involve, respectively, W-, X-, and Y-cells in the retina and the lateral geniculate nucleus. In this study, we investigated the morphology of those neurons in the C laminae of the lateral geniculate nucleus that receive input from retinal W-cells. Micropipettes filled with horseradish peroxidase (HRP) were used to record the responses of single geniculate neurons identified as W-, X-, or Y-cells. Five W-cells in the C laminae then were stained intracellularly by impalement of the cell with the microelectrode followed by iontophoresis of HRP. Each of these neurons has a small to medium size soma and fine dendrites oriented roughly parallel to the plane of the geniculate laminar borders. These geniculate W-cells differ among themselves mainly in the detail of their dendritic processes. Three of these cells have virtually no dendritic appendages, while the other two have complex appendages not previously reported among neurons in the C laminae. Also, the degree of horizontal orientation of the dendrites differs considerably among these cells. Overall, the morphology of these W-cells is generally consistent with the class 4 cell briefly described by Guillery (Guillery, R. W. (1966) J. Comp. Neurol. 128: 21-50), and consequently, our data indicate that class 4 neurons are the morphological correlate of neurons physiologically classified as W-cells. Since greater morphological detail is presented by these HRP-filled cells than by previous Golgi-impregnated preparations, we can describe more completely the morphology of class 4 cells.

Animals↗

PubMed1978

Retinal organisation in goldeye and mooneye (Teleostei: hiodontidae).

This paper presents the results of a comparative investigation of the retinas of two Hiodontids, the goldeye (Hiodon alosoides) and the Mooneye (H. tergisus) employing light and electron microscopy, cell isolation techniques as well as microspectrophotometry. Contrary to the observations of previous workers these species possess a duplex retina. The photoreceptors are bundled in groups of 20 rods and 20 cones. They exhibit features which have hitherto not been observed in vertebrates. These are a) an ellipsoid divided in two parts by the myoid: b) tubules in cone outer segments and, c) large "lateral sacs" (accessory outer segments). Cones are immobile but the rods and epithelial pigment are capable of movement (retinomotor responses). The prominent reflecting layer consists of cuboid and rod-like crystals composed of uric acid. The inner layers are made up of three tiers of large horizontal cells, one of amacrine cells and scarce bipolar and ganglion cells. Bundle density is 1 700 per sq. mm. Roughly, one receptor bundle projects onto one bipolar and one ganglion cell suggesting that each bundle acts as a functional unit. The visual pigment of the mooneye absorbs maximally at 535 +/- 2 nm, and is based on vitamin A2 (porphyropsin). We suggest that all non deep-sea fishes with bundled receptors have duplex retinas and the adaptive mechanisms for vision in turbid waters are based on different morphological means as illustrated by the comparison with Stizostedion.

Adaptation, Ocular↗

PubMed1990

Spatial resolution across the macaque retina.

Grating acuity was measured as a function of eccentricity from the fovea in two macaques. A vertical-horizontal orientation discrimination was used to determine acuity, and the retinal locus of the test grating was controlled by training them to fixate a spot placed at various distances from the stimulus. Their head was fixed in place and fixation was monitored with a scleral search coil. The acuity of monkeys across the retina was similar to that previously measured in human subjects, reaching a peak of about 38 c/deg at the fovea, and decreasing about 10-fold by 30 deg eccentricity. Acuity was slightly higher in the temporal than in the nasal visual field. The shape of the acuity-eccentricity function suggested a dependence on cone density near the fovea, and on the density of P ganglion cells at eccentricities beyond 10 deg. Existing physiological data suggest the possibility that macaque acuity may also be limited in part by spatial averaging across the receptive field of retinal ganglion cells.

Animals↗

PubMed1992

Visual deprivation fails to reduce calbindin 28kD or GABA immunoreactivity in the rhesus monkey superior colliculus.

Antibody labeling of the calcium-binding protein calbindin 28kD (CaBP) and gamma-aminobutyric acid (GABA) is altered by short-term monocular deprivation in the lateral geniculate nucleus and visual cortex of adult primates. It is not known whether these alterations occur in other subcortical visual structures. We therefore have examined antibody labeling to CaBP and GABA in the superior colliculus (SC) of visually deprived Rhesus monkeys. One group was monocularly enucleated as adults. The other monkeys experienced different types of monocular and binocular deprivation from birth, including occlusion of one eye, and/or surgically induced aphakia, optically corrected with extended-wear contact lenses, or an intraocular lens implant. Some of these monkeys also had one eye enucleated prior to perfusion. In the SC of normal monkeys, CaBP-immunoreactive neurons formed three laminar tiers within SC, one within the zonal layer (ZL) and upper superficial gray layer (SGL), another bridging the optic and intermediate gray layers, and a third within the deep gray layer. CaBP neurons within the upper tier had small pyriform or stellate morphologies while those in the deeper tiers were slightly larger neurons, most with a stellate morphology. GABA-immunoreactive neurons were densely distributed within the SGL and more sparsely distributed within the deeper layers. These cells were mostly small neurons with horizontal, pyriform, or stellate morphologies. Neither monocular enucleation nor occlusion nor aphakia combined with continuous occlusion of the fellow eye produced any visible reduction in antibody labeling in cells or neuropil within the SC. Full-field measures of labeling intensity (optical density) within the ZL and upper SGL revealed no consistent differences between the SC contralateral or ipsilateral to the affected eye in either CaBP- or GABA-labeled sections. Measures of the optical density, number, and size of labeled neurons also showed no consistent effects of enucleation and/or occlusion. We therefore conclude that the retino-geniculostriate and retino-collicular systems differ in their response to deprivation which is likely due to the significant overlap of retinal axons from the two eyes that occurs in the SC of the Rhesus monkey.

Animals↗

PubMed1989

Changing distribution of GABA-like immunoreactivity in pigeon visual areas during the early posthatching period and effects of retinal removal on tectal GABAergic systems.

The distribution of GABA-like immunoreactivity in the pigeon visual system was studied during the first 9 days after hatching using a mouse monoclonal antibody, mAb 3A12, to glutaraldehyde linked GABA (Matute & Streit, 1986). GABA-like immunoreactivity was seen in cell bodies as well as in neuropil at the level of both the retina and central visual regions at any posthatching age. However, the distribution of putative GABAergic cells and processes varied with age reaching the adult pattern at around 9 days. As a general observation, almost no cell bodies in the retina (except for some perikarya in the ganglion cell layer) were labeled at hatching but densely packed immunostained processes were present in the inner plexiform layer. During the next few days, GABA-immunoreactive amacrine and horizontal cells appeared and the adult distribution of GABA-like immunoreactivity was reached at around 9 days. In the other visual regions examined, the general trend in the variation of GABA-like immunoreactivity included: (1) a progressive decrease in the density of immunostained cell bodies and (2) an almost parallel increase in the concentration of stained neuropil. Since in pigeons the adult organization of visual pathways and the final distribution of putative GABAergic systems are reached at around the same age, we suggest the possibility that incoming ganglion cell axons play a role in regulating the distribution of GABA-like immunoreactivity in visual areas. This hypothesis is supported by the fact that the distribution of GABA-like immunoreactivity in the superficial layers of the optic tectum was altered following ablation of the contralateral retina immediately after hatching.

Animals↗

PubMed1995

Distribution and spatial geometry of dopamine interplexiform cells in the retina. II. External arborizations in the adult rat and monkey.

The morphology and distribution of dopaminergic interplexiform cells in adult rat and monkey retinas were analyzed to determine any correlation with the function of dopamine in the outer retinal layers. The retinas were processed as whole mounts for tyrosine hydroxylase immunohistochemistry. There was a network formed by the sclerally directed processes of interplexiform cells in the inner nuclear, outer plexiform, and outer nuclear layers running throughout the retina. Their density was higher in the superior retina than in the inferior retina of the rat and was especially high in the superior temporal quadrant. The external network in this quadrant was significantly less dense in the monkey than in the rat, as are the interplexiform cells. The somata of interplexiform and other dopaminergic cells were about the same size in both rats and monkeys. Computer-assisted reconstruction of external arborizations of individual cells showed that external processes lay very close to horizontal and photoreceptor cells and also to blood capillaries. Because they were long, thin, and highly varicose; branched at right angles; and often arose from an axon hillock, the external processes were identified as axons. Therefore, we define the dopaminergic interplexiform cells as multiaxonal neurons, with at least one outwardly directed axon that reaches the outer plexiform layer. The function of the network of external processes from the interplexiform dopaminergic cells is discussed in terms of modulating the release of dopamine to external layers.

Animals↗

PubMed2004

Differential effects of ischemia/reperfusion on amacrine cell subtype-specific transcript levels in the rat retina.

Transient retinal ischemia induces loss of retinal ganglion cells, supporting the hypothesis that ischemic conditions contribute to the induction and progression of glaucoma. However, after 60 min of ischemia, also amacrine cells are lost from the inner nuclear layer. The main goal was to determine the relative vulnerability of various amacrine subpopulations by measuring the levels of transcripts that are known to be specifically expressed by different amacrine subpopulations. A 60-min ischemic period was administered to the rat eye by raising the intraocular pressure, followed by a reperfusion period lasting between 2 h and 4 weeks. Total RNA was isolated from the whole retina and expression levels were assessed by real-time quantitative polymerase chain reaction (qPCR). Retinal ischemia/reperfusion has differential effects on the levels of the various transcripts. Three main patterns of changes were identified. (i) A gradual decrease of transcript level without recovery was observed for parvalbumin; this transcript is expressed by the glycinergic AII cells. (ii) A gradual reduction to different levels at 72 h of reperfusion followed by a partial or complete recovery (glycine transporter 1, glutamate decarboxylase, calretinin, and several other transcripts). The glycinergic amacrine cell markers recovered to 65-75% of the control level, while the main GABAergic markers had completely recovered at 4 weeks. (iii) No significant changes of transcript levels were found for markers of several smaller GABAergic subpopulations [including substance P (Tac1), somatostatin, and others]. Expression levels of photoreceptor-, horizontal cell-, and bipolar cell-specific transcripts were not altered. These patterns were confirmed by a cluster analysis of the data. Based on gene expression levels, it may be concluded that amacrine cells are vulnerable to ischemic insults and that the glycinergic amacrine cells are relatively more sensitive to ischemia than the GABAergic population. In particular, the extensive loss of the parvalbumin-containing AII amacrine cells, which serve in the rod pathway, may have functional implications for vision under scotopic conditions. In the accompanying paper [F. Dijk and W. Kamphuis, An immunocytochemical study on specific amacrine subpopulations in the rat retina after ischemia, Brain Res. (2004).], the results are evaluated at the protein level by immunostaining for a selection of the amacrine cell markers.

Amacrine Cells↗