Morphology of dopaminergic amacrine cells in the mouse retina: Independence from homotypic interactions

To determine the role of homotypic interactions between neighboring dopaminergic amacrine (DA) cells upon dendritic morphogenesis, the morphology of single cells was examined relative to the positioning of all neighboring homotypic cells. For each labeled cell, the dendritic field was reconstructed, its Voronoi domain was calculated, and the two were related. The dendritic fields of DA cells were observed to be large, sparse, and highly irregular. Dendrites readily overlapped those of neighboring cells, showing no evidence for dendritic tiling or inter‐digitation consistent with homotypic repulsion or avoidance. Furthermore, a direct comparison of dendritic field area with the Voronoi domain area of the same cell showed no evidence for dendritic growth being constrained or biased by the local distribution of homotypic neighbors in wild‐type retinas. A comparison of the processes of adjacent filled cells confirmed their immediate proximity to one another within the inner plexiform layer, indicating that they do not engage in mutual avoidance by coursing at different depths. Together, these results suggest that the morphogenesis of DA cells is independent of homotypic interactions. However, in the absence of the pro‐apoptotic Bax gene, which yields a fourfold increase in DA cell number, a small but significant reduction in dendritic field size was obtained, although not so great as would be predicted by the increase in density. The present results are considered in light of recent studies on the role of cell adhesion molecules expressed by developing DA cells. J. Comp. Neurol. 518:1220–1231, 2010. © 2009 Wiley‐Liss, Inc.     

Immunocytochemical staining of AII-amacrine cells in the rat retina with antibodies against parvalbumin

The rod dominated rodent retina is the preferred tissue for in vitro studies of mammalian retinal physiology and pharmacology. The rod pathway through the rat retina was investigated, therefore, in order to find out whether its organization follows the mammalian “plan.” AII-amacrine cells of the rat retina were injected with Lucifer Yellow to characterize the morphology of this bistratified interneuron of the rod pathway. When sections or whole mounts of the rat retina were stained with antibodies against the calcium binding protein parvalbumin (PV), two different amarcine cell types were labeled: the AII-amacrine cell and a widefield amacrine cell. They occur at a ratio of 12:1. Weak label was also observed in ganglion cells. The density of PV-labeled AII-cells decreases from approximately 7,000 cells/mm² in upper central retina to 2,000 cells/mm² in peripheral retina. Their cell bodies form a regular mosaic, and the dendritic arbors of three neighbouring AII-amacrine cells overlap (coverage of 3). © Wiley-Liss, Inc.     

Characterization of secretagogin‐immunoreactive amacrine cells in marmoset retina

The retina contains at least 30 different types of amacrine cells but not many are well characterized. In the present study the calcium‐binding protein secretagogin was localized in a population of regular and displaced amacrine cells in the retina of the common marmoset Callithrix jacchus. Irrespective of their soma location, the dendrites of secretagogin amacrine cells occupy strata 2, 3, and 4 of the inner plexiform layer, between the two bands formed by cholinergic amacrine cells. Segretagogin amacrine cells are also immunopositive to antibodies against glutamic acid decarboxylase, suggesting that they use γ‐aminobutyric acid (GABA) as their neurotransmitter. The spatial density of secretagogin amacrine cells decreases from a peak of about 400 cells/mm² near 1 mm eccentricity to less than 100 cells/mm² in peripheral retina; these densities account for about 1% of amacrine cells in the inner nuclear layer and for up to 27% of displaced amacrine cells. The cell bodies form a regular mosaic, suggesting that they constitute a single amacrine cell population. Secretagogin cells have varicose dendrites, which are decorated with small spines. Intracellular injection of DiI into secretagogin cells revealed an average dendritic field diameter of 170 μm and an average coverage factor of 3.2. In summary, secretagogin cells in marmoset retina are medium‐field amacrine cells that share their stratification pattern with narrow‐field amacrine cells and their neurotransmitter with wide‐field amacrine cells. They may mediate spatial inhibition spanning the centralmost (on and off) bands of the inner plexiform layer. J. Comp. Neurol. 522:435–455, 2014. © 2013 Wiley Periodicals, Inc.     

Somal positioning and dendritic growth of horizontal cells are regulated by interactions with homotypic neighbors

Retinal neurons extend their dendritic fields to achieve a degree of dendritic overlap with homotypic neighbors that is cell-type specific. How these neurons regulate their dendritic growth is unclear. The dendritic field of a retinal horizontal cell varies inversely with horizontal cell density across different strains of mice, suggesting that proximity to neighboring cells regulates dendritic growth. To test this directly, we have employed the Cre-loxP conditional gene targeting strategy to achieve inactivation of Lim1 function in developing horizontal cells. Through this approach, Lim1 function was prevented within a subset of horizontal cells that in turn fail to migrate to the horizontal cell layer and differentiate normally. For those remaining horizontal cells with Lim1 intact (about half of the normal population in these mice), we show that they spread themselves out tangentially and differentiate a dendritic morphology that is essentially normal but for the fact that it has nearly doubled in area. Such larger horizontal cells, sampling from an area of retina containing twice their normal afferent number, differentiate a dendritic field with nearly double the number of higher order branches and terminal clusters. These results demonstrate directly that positioning and dendritic growth are regulated by interactions with homotypic neighbors, whereas afferents instruct the differentiation of dendritic patterning.     

Morphology and physiology of the polyaxonal amacrine cells in the rabbit retina.

We examined the morphology and physiological response properties of the axon-bearing, long-range amacrine cells in the rabbit retina. These so-called polyaxonal amacrine cells all displayed two distinct systems of processes: (1) a dendritic field composed of highly branched and relatively thick processes and (2) a more extended, often sparsely branched axonal arbor derived from multiple thin axons emitted from the soma or dendritic branches. However, we distinguished six morphological types of polyaxonal cells based on differences in the fine details of their soma/dendritic/axonal architecture, level of stratification within the inner plexiform layer (IPL), and tracer coupling patterns. These morphological types also showed clear differences in their light-evoked response activity. Three of the polyaxonal amacrine cell types showed on-off responses, whereas the remaining cells showed on-center responses; we did not encounter polyaxonal cells with off-center physiology. Polyaxonal cells respected the on/off sublamination scheme in that on-off cells maintained dendritic/axonal processes in both sublamina a and b of the IPL, whereas processes of on-center cells were restricted to sublamina b. All polyaxonal amacrine cell types displayed large somatic action potentials, but we found no evidence for low-amplitude dendritic spikes that have been reported for other classes of amacrine cell. The center-receptive fields of the polyaxonal cells were comparable to the diameter of their respective dendritic arbors and, thus, were significantly smaller than their extensive axonal fields. This correspondence between receptive and dendritic field size was seen even for cells showing extensive homotypic and/or heterotypic tracer coupling to neighboring neurons. These data suggest that all polyaxonal amacrine cells are polarized functionally into receptive dendritic and transmitting axonal zones.     

Morphology and distribution of neurons immunoreactive for substance P in the turtle retina

Immunocytochemical staining procedures with the HRP-complexed antibody to substance P have been carried out on the turtle retina. Examination by light microscopy of wholemount retinas has allowed us to evaluate the morphology and distribution of the substance P immunoreactive cell types. Two amacrine cell types and two or more ganglion cell types are stained in our hands. Type A amacrines are tri-stratified wide-field amacrines. They have their major dendrites in S1 and S3 of the inner plexiform layer and they emit fine dendrites from the major dendrites that end in varicose boutons in S5 on and around cell bodies in the ganglion cell layer. Some of the dendrites in S1 radiate out in axon-like fashion for 1 mm across the retina. The type B amacrine cells are small to medium-field in dendritic extent. They have smaller cell bodies than type A and a single or, at most, two primary dendrites that pass directly to S3 before branching profusely into an intricate net-like dendritic field. The ganglion cells that are stained with substance P antibodies appear to be of several types but their exact morphologies are in doubt because only portions of their major dendrites are stained. Substance P immunoreactive axons are clearly seen to project from the cell bodies to the optic nerve head and axons are stained in the optic nerve itself. The substance P-stained ganglion cells occur in an irregular distribution that reaches a peak density in an elongated band parallel to and 1 mm below the visual streak. The type B amacrine cells reach a maximum density in the visual streak and are distributed in a highly regular mosaic decreasing in density in elliptical isodensity contours from the visual streak. In contrast the type A amacrine cells are rare or absent in the streak, being located in an irregular mosaic in peripheral retina.     

Characterization of an amacrine cell type of the mammalian retina immunoreactive for vesicular glutamate transporter 3

Immunocytochemical staining of vertical sections through rat, mouse, and macaque monkey retinae with antibodies against the vesicular glutamate transporter vesicular glutamate transporter 3 (vGluT3) showed a sparse population of amacrine cells. The labeled cells had similar appearances in the three species and probably represent homologous types. They were studied in detail in the rat retina. The thin varicose dendrites of vGluT3 amacrine cells formed a convoluted dendritic tree of approximately 100 microm in diameter that was bistratified in the center of the inner plexiform layer. The dendrites of vGluT3 cells were squeezed between the two strata of cholinergic dendrites. The density of vGluT3 cells was measured in retinal wholemounts and increased from 200/mm2 in peripheral retina to 400/mm2 in central retina, accounting for about 1% of all amacrine cells in the rat retina. The vGluT3 cells had a two- to threefold dendritic overlap, and their cell bodies formed a regular mosaic, suggesting they represent a single type of amacrine cell. The vGluT3 amacrine cells expressed glycine and glycine transporter 1 (GlyT1) but not the vesicular glycine transporter (vesicular inhibitory amino acid transporter). They also expressed glutamate; hence, there is the possibility that, comparable to cholinergic amacrine cells, they are "dual transmitter" amacrine cells. The synaptic input of vGluT3 cells was studied by electron microscopy. They received input from bipolar cells at ribbon synapses and from other amacrine cells at conventional synapses. The types of bipolar cells possibly involved with vGluT3 cells were demonstrated by double labeling sections for vGluT3 and the calcium-binding protein CaB5. The axon terminals of type 3 and 5 bipolar cells costratified with vGluT3 dendrites, and it is possible that vGluT3 cells have ON and OFF light responses.     

Age-related alterations in neurons of the mouse retina

The behavioral consequences of age-related alterations in neural function are well documented, but less is known about their cellular bases. To characterize such changes, we analyzed 14 molecularly identified subsets of mouse retinal projection neurons (retinal ganglion cells or RGCs) and interneurons (amacrine, bipolar, and horizontal cells). The retina thinned but expanded with age, maintaining its volume. There was minimal decline in the number of RGCs, interneurons, or photoreceptors, but the diameter of RGC dendritic arbors decreased with age. Together, the increased retinal area and the decreased dendritic area may lead to gaps in RGC coverage of the visual field. Axonal arbors of RGCs in the superior colliculus also atrophied with age, suggesting that the relay of visual information to central targets may decline over time. On the other hand, the laminar restriction of RGC dendrites and the interneuronal processes that synapse on them were not detectably disturbed, and RGC subtypes exhibited distinct electrophysiological responses to complex visual stimuli. Other neuronal types aged in different ways: amacrine cell arbors did not remodel detectably, whereas horizontal cell processes sprouted into the photoreceptor layer. Bipolar cells showed arbor-specific alterations: their dendrites sprouted but their axons remained stable. In summary, retinal neurons exhibited numerous age-related quantitative alterations (decreased areas of dendritic and axonal arbors and decreased density of cells and synapses), whereas their qualitative features (molecular identity, laminar specificity, and feature detection) were largely preserved. Together, these data reveal selective age-related alterations in neural circuitry, some of which could underlie declines in visual acuity.     

Characterization of small-field bistratified amacrine cells in macaque retina labeled by antibodies against synaptotagmin-2

Macaque retinae were immunostained with monoclonal antibodies directed against the protein synaptotagmin‐2 (Syt2). Syt2 was localized in a population of small‐field amacrine cells, whose cell bodies formed a regular mosaic within the inner nuclear layer, indicating they represent a single amacrine cell type. The labeled amacrine cells had a bistratified appearance with a dense dendritic plexus in the OFF‐layer and only a few lobular processes extending into the ON‐layer of the inner plexiform layer, similar to A8 amacrine cells described in cat and human retina. Syt2‐labeled cells were immunoreactive for glycine but lacked immunoreactivity for γ‐aminobutyric acid (GABA), suggesting they use glycine as their neurotransmitter. The density of these cells increases from ～200/mm² in peripheral retina to ～1,400/mm² in central retina. Their bipolar cell input was studied by immunolabeling experiments using various bipolar cell markers combined with CtBP2, a marker of presynaptic ribbons. Our data show that Syt2‐labeled amacrine cells receive input from both OFF and ON cone bipolar cells, as well as from rod bipolar cells. The OFF input is dominated by the diffuse bipolar cell DB1 (44%) and the OFF midget bipolar cell (38%). Here we describe a population of bistratified small‐field amacrine cells closely resembling A8 amacrine cells and their cone‐dominated bipolar cell input. J. Comp. Neurol. 521:709–724, 2013. © 2012 Wiley Periodicals, Inc.     

Homotypic regulation of neuronal morphology and connectivity in the mouse retina

The establishment of neuronal circuitry during development relies upon the action of cell-intrinsic mechanisms that specify neuronal form as well as plastic processes that require the transmission of neural activity between afferents and their targets. Here, we examine the role of interactions between neighboring like-type cells within the mouse retina upon neuronal differentiation and circuit formation. Two different genetically modified mouse models were used to modulate the density of homotypic neighbors, the Type 7 cone bipolar cells, without affecting the density of their afferents, the cone photoreceptors. We demonstrate a corresponding plasticity in dendritic field area when the density of Type 7 cone bipolar cells is elevated or reduced. In accord with this variation in dendritic field area across an invariant population of afferents, individual Type 7 cone bipolar cells are also shown to modulate the number of cone pedicles contacted without varying the number of contacts at each cone pedicle. Analysis of developing Type 7 cone bipolar cells reveals that the dendritic tiling present in maturity is achieved secondarily, after an initial stage of dendritic overlap, when the dendritic terminals are stratified at the level of the cone pedicles but are not localized to them. These results demonstrate a conspicuous developmental plasticity in neural circuit formation independent of neural activity, requiring homotypic interactions between neighboring cells that ultimately regulate connectivity within the retina.     

Dendritic spread and functional coverage of starburst amacrine cells

The network of starburst amacrine cells plays a fundamental role in the neural circuitry underlying directional selectivity within the retina. Individual sectors of the starburst dendritic field are directionally selective by virtue of a mutually inhibitory relationship between starburst amacrine cells with overlapping dendrites. These features of the starburst amacrine cell network suggest that starburst cells regulate their dendritic overlap to ensure a uniform coverage of the retinal surface. The present study has compared the dendritic morphology of starburst amacrine cells in two different strains of mice that differ in starburst amacrine cell number. The A/J (A) strain contains about one-quarter fewer starburst amacrine cells than does the C57BL/6J (B6) strain, although the mosaics of starburst amacrine cells in both strains are comparably patterned. Dendritic field size, however, does not compensate for the difference in density, the A strain having a slightly smaller dendritic field relative to the B6 strain, yielding a significantly larger dendritic coverage factor for individual cells in the B6 strain. The area of the distal (output) annulus of the dendritic field occupies a comparable proportion of the overall field area in the two strains, but overlapping annuli establish a finer meshwork of co-fasciculating processes in the B6 strain. These results would suggest that the architecture of the dendritic network, rather than the overall size of the dendritic field, is dependent on the density of starburst amacrine cells.     

Morphology and distribution of catecholaminergic amacrine cells in the cone-dominated tree shrew retina.

The tree shrew (Tupaia belangeri) has a cone-dominated retina with a rod proportion of only 5%. This is in contrast to the usual mammalian pattern of rod-dominated retinae. Rod bipolar cells are present at relatively low densities in the tree shrew retina, suggesting that a reduced, but normal, rod pathway might be preserved. The present study investigated another common constituent of the rod pathway, the dopaminergic amacrine cells, and analysed their morphology and distribution by light and electron microscopy. Catecholaminergic (presumed dopaminergic) amacrine cells were labelled with an antibody against tyrosine hydroxylase (TH). Intense TH-immunoreactivity was found in perikarya and dendrites of a uniform amacrine cell population. TH-immunoreactive amacrine cell density varies across the retina from 10 cells/mm2 in the periphery to 40 cells/mm2 in more central regions (mean cell density about 25 cells/mm2). The relatively large cell bodies are located exclusively in the innermost part of the inner nuclear layer. The dendrites form a dense plexus at the border between the inner plexiform layer and the inner nuclear layer. The finer dendritic processes contain many varicosities and form characteristic dendritic "rings" like those seen in other mammals. TH-immunoreactive processes also run between cell bodies in the vitread inner nuclear layer; a few extend into the sclerad inner nuclear layer and occasionally reach the outer plexiform layer (possible interplexiform cells). A few TH-immunoreactive processes are seen in the middle of the inner plexiform layer. Electron microscopy of TH-immunoreactive processes revealed conventional synapses onto somata and processes of unlabelled amacrine cells.     

Morphology and tracer coupling pattern of alpha ganglion cells in the mouse retina

Alpha cells are a type of ganglion cell whose morphology appears to be conserved across a number of mammalian retinas. In particular, alpha cells display the largest somata and dendritic arbors at a given eccentricity and tile the retina as independent on- (ON) and off-center (OFF) subtypes. Mammalian alpha cells also express a variable tracer coupling pattern, which often includes homologous (same cell type) coupling to a few neighboring alpha cells and extensive heterologous (different cell type) coupling to two to three amacrine cell types. Here, we use the gap junction-permeant tracer Neurobiotin to determine the architecture and coupling pattern of alpha cells in the mouse retina. We find that alpha cells show the same somatic and dendritic architecture described previously in the mammal. However, alpha cells show varied tracer coupling patterns related to their ON and OFF physiologies. ON alpha cells show no evidence of homologous tracer coupling but are coupled heterologously to at least two types of amacrine cell whose somata lie within the ganglion cell layer. In contrast, OFF alpha cells are coupled to one another in circumscribed arrays as well as to two to three types of amacrine cell with somata occupying the inner nuclear layer. We find that homologous coupling between OFF alpha cells is unaltered in the connexin36 (Cx36) knockout (KO) mouse retina, indicating that it is not dependent on Cx36. However, a subset of the heterologous coupling of ON alpha cells and all the heterologous coupling of OFF alpha cells are eliminated in the KO retina, suggesting that Cx36 comprises most of the junctions made with amacrine cells.     

Neuropeptide Y-like immunoreactive amacrine cells in the retina ofBufo marinus

Neuropeptide Y-like immunoreactive (NPY-LI) amacrine cells of theBufo marinus retina were morphologically characterized, and their retinal distribution was established using immunohistochemistry on retinal wholemount preparations and sectioned material. The somas of NPY-LI amacrine cells were situated in the innermost part of the inner nuclear layer and their dendrites branched primarily in the scleral sublamina of the inner plexiform layer. A subgroup of the NPY-LI cells had dendrites in both the scleral and vitreal sublamina. All immunoreactive cells had large dendritic fields (average 0.5 mm²) that resulted in a high dendritic overlap across the retina. NPY-LI amacrine cells were evenly distributed across the retina, with an average density of 30 cells/mm², although higher densities were observed at regions adjacent to the ciliary margin. The dendritic field size of the NPY-LI cells, together with the previously characterized substance P-like immunoreactive (SP-LI) amacrine cells, indicates that they belong to the class of wide-field amacrine cells. However, unlike the SP-LI neurons whose dendrites branch in the vitreal sublamina of the inner plexiform layer, the dendrites of the majority of the NPY-LI neurons branch in the scleral sublamina.     

Development of catecholaminergic, indoleamine-accumulating and NADPH-diaphorase amacrine cells in rabbit retinae.

We have investigated the ontogeny of four classes of amacrine cells in the rabbit retina. In particular, the distribution, number, soma diameter, dendritic field diameter, and pattern of dendritic stratification were studied in catecholaminergic (CA) and indoleamine-accumulating (IA) amacrines and in two classes of nicotinamide adenine dinucleotide phosphate (NADPH) diaphorase amacrine cells. The first CA and IA cells are observed on the 27th postconceptional day (27PCD) and the first NADPH-diaphorase cells on 28PCD. These first cells are concentrated in the central part of the visual streak, and at subsequent ages, cells in this part of the streak have larger somata and more mature dendritic fields than those elsewhere, supporting the notion that the peak density region is a developmentally advanced part of the retina. Throughout development, amacrine cells of all classes are concentrated in the visual streak, with their density reaching minima at the superior and inferior retinal margins. As their total number increases, the difference in cell density between the streak and the periphery decreases, presumably because proportionately more cells are added at the periphery. Their total number peaks around 42PCD, followed by a decline of 12-31% to adult values. Once the peak number of cells has been reached, the difference in cell density between the streak and periphery begins to increase. The rate of this increase is closely correlated with the increase in retinal area. This redistribution of amacrine cells, as well as a greater expansion of their dendritic fields in peripheral retina, is almost certainly the product of nonuniform retinal expansion.     

The p57Kip2 cyclin kinase inhibitor is expressed by a restricted set of amacrine cells in the rodent retina

Amacrine cells in the vertebrate retina can be grouped according to morphology into distinct types, which are organized into characteristic mosaics. Each type is believed to perform a unique role in visual signal processing. Neurotransmitters and calcium binding proteins have served as important markers for amacrine cell populations, yet many types remain to be characterized at the molecular level. We have found that a cyclin kinase inhibitor, p57Kip2, is expressed in a restricted group of amacrine cells in the inner nuclear layer (INL) and ganglion cell layer (GCL) of the rodent retina. Whole-mount antibody staining revealed that the p57Kip2 amacrine cells are evenly distributed across the retina with a density of 1654 +/- 63 cells/mm(2) in the INL and 994 +/- 26 cells/mm(2) in the GCL. These amacrine cells accumulate the major inhibitory neurotransmitter gamma-aminobutyric acid (GABA) but do not accumulate high levels of glycine. In addition, p57Kip2 immunoreactivity does not colocalize with any of the previously identified amacrine cell markers including calbindin, calretinin, parvalbumin, choline acetyltransferase, and tyrosine hydroxylase. To determine whether the p57Kip2 population of amacrine cells is organized into a regular or a random mosaic, nearest neighbor analysis was performed for both the INL and GCL populations. Results from this analysis demonstrated that the p57Kip2-immunoreactive amacrine cells are randomly organized and therefore they are likely to constitute two or more distinct populations. This new molecular marker will serve as a useful tool for future studies on the development and function of amacrine cells in the vertebrate retina.     

Neuropeptide Y-like immunoreactive amacrine cells in the retina of Bufo marinus

Neuropeptide Y-like immunoreactive (NPY-LI) amacrine cells of the Bufo marinus retina were morphologically characterized, and their retinal distribution was established using immunohistochemistry on retinal wholemount preparations and sectioned material. The somas of NPY-LI amacrine cells were situated in the innermost part of the inner nuclear layer and their dendrites branched primarily in the scleral sublamina of the inner plexiform layer. A subgroup of the NPY-LI cells had dendrites in both the scleral and vitreal sublamina. All immunoreactive cells had large dendritic fields (average 0.5 mm2) that resulted in a high dendritic overlap across the retina. NPY-LI amacrine cells were evenly distributed across the retina, with an average density of 30 cells/mm2, although higher densities were observed at regions adjacent to the ciliary margin. The dendritic field size of the NPY-LI cells, together with the previously characterized substance P-like immunoreactive (SP-LI) amacrine cells, indicates that they belong to the class of wide-field amacrine cells. However, unlike the SP-LI neurons whose dendrites branch in the vitreal sublamina of the inner plexiform layer, the dendrites of the majority of the NPY-LI neurons branch in the scleral sublamina.     

Synaptology of physiologically identified ganglion cells in the cat retina: A comparison of retinal X- and Y-cells

It has long been known that a number of functionally different types of ganglion cells exist in the cat retina, and that each responds differently to visual stimulation. To determine whether the characteristic response properties of different retinal ganglion cell types might reflect differences in the number and distribution of their bipolar and amacrine cell inputs, we compared the percentages and distributions of the synaptic inputs from bipolar and amacrine cells to the entire dendritic arbors of physiologically characterized retinal X- and Y- cells. Sixty-two percent of the synaptic input to the Y-cell was from amacrine and bipolar cells. We found no significant difference in the distributions of bipolar or amacrine cell inputs to X- and Y- cells, or ON-center and OFF-center cells, either as a function of dendritic branch order or distance from the origin of the dendritic arbor. While, on the basis of these data, we cannot exclude the possibility that the difference in the proportion of bipolar and amacrine cell input contributes to the functional differences between X- and Y- cells, the magnitude of this difference, and the similarity in the distributions of the input from the two afferent cell types, suggest that mechanisms other than a simple predominance of input from amacrine or bipolar cells underlie the differences in their response properties. More likely, perhaps, is that the specific response features of X- and Y- cells originated in differences in the visual responses of the bipolar and amacrine cells that provides their input, or in the complex synaptic arrangements found among amacrine and bipolar cell terminals and dendrites of specific types of retinal ganglion cells. © 1994 Wiley-Liss, Inc.     

AII amacrine cells in the inner nuclear layer of bat retina: identification by parvalbumin immunoreactivity

The purpose of this investigation is to characterize parvalbumin-immunoreactive (PV-IR) amacrine cells in bat retina through immunocytochemistry, quantitative analysis, and confocal microscopy. PV immunoreactivity was present in ganglion cell and inner nuclear layers. The regular distribution of PV-IR neurons, the inner marginal locations of their cell bodies in the inner nuclear layers, and the distinctive bilaminar morphologies of their dendritic arbors in the inner plexiform layers suggested that these PV-IR cells were AII amacrine cells. PV-IR neurons were double labeled forcalretinin, a marker for AII cells. These results indicate that PV antibodies can be used to label AII cells selectively in bats. The existence of AII cells suggests that bats have retinas involved in both rod-driven and cone-driven signals.