Neuropeptide Y (NPY) immunoreactive neurons in the retina of different species

Neurons displaying Neuropeptide Y (NPY) immunoreactivity were found among amacrine cells in the retina of baboon, pig, cat, pigeon, chicken, frog, trout, carp and goldfish. The immunoreactive cell bodies were located in the middle and the innermost cell rows of the inner nuclear layer with processes forming one, two or three more or less well-defined sublayers in the inner plexiform layer. The location and the density of the sublayers varied with the species investigated. In the frog retina, bipolar-like cell bodies were found in the middle of the inner nuclear layer as well as sparsely occurring ovoid cell bodies in the ganglion cell layer. Like the amacrine cells, these cells emitted processes ramifying in three sublayers in the inner plexiform layer.     

Neuropeptide Y (NPY) immunoreactive neurons in the retina of different species

Summary Neurons displaying Neuropeptide Y (NPY) immunoreactivity were found among amacrine cells in the retina of baboon, pig, cat, pigeon, chicken, frog, trout, carp and goldfish. The immunoreactive cell bodies were located in the middle and the innermost cell rows of the inner nuclear layer with processes forming one, two or three more or less well-defined sublayers in the inner plexiform layer. The location and the density of the sublayers varied with the species investigated. In the frog retina, bipolar-like cell bodies were found in the middle of the inner nuclear layer as well as sparsely occurring ovoid cell bodies in the ganglion cell layer. Like the amacrine cells, these cells emitted processes ramifying in three sublayers in the inner plexiform layer.     

Somatostatin and VIP neurons in the retina of different species

Neurons displaying somatostatin or vasoactive intestinal polypeptide (VIP) immunoreactivity were detected among the amacrine cells in the retina of baboon, cynomolgus monkey, squirrel monkey, cow, pig, cat, rabbit, guinea-pig, rat, mouse, frog and goldfish. Generally, immunoreactive cell bodies were located in the inner nuclear layer with processes ramifying in three more or less well-defined sublayers in the inner plexiform layer. The density of the sublayers and their location varied with the peptide and species investigated. In most cases there was a sublayer in the outermost part (Ramon y Cajal's sublamina 1) of the inner plexiform layer and this sublayer was usually the best developed. In some species a few somatostatin fibres were also detected in the outer plexiform layer, suggesting that some interplexiform cells contain somatostatin. In the baboon VIP was found exclusively in interstitial amacrine cells which have their cell bodies and processes entirely within the inner plexiform layer.     

Somatostatin and VIP neurons in the retina of different species

Summary Neurons displaying somatostatin or vasoactive intestinal polypeptide (VIP) immunoreactivity were detected among the amacrine cells in the retina of baboon, cynomolgus monkey, squirrel monkey, cow, pig, cat, rabbit, guinea-pig, rat, mouse, frog and goldfish. Generally, immunoreactive cell bodies were located in the inner nuclear layer with processes ramifying in three more or less well-defined sublayers in the inner plexiform layer. The density of the sublayers and their location varied with the peptide and species investigated. In most cases there was a sublayer in the outermost part (Ramon y Cajal's sublamina 1) of the inner plexiform layer and this sublayer was usually the best developed. In some species a few somatostatin fibres were also detected in the outer plexiform layer, suggesting that some interplexiform cells contain somatostatin. In the baboon VIP was found exclusively in interstitial amacrine cells which have their cell bodies and processes entirely within the inner plexiform layer.     

Neurofibrillar long-range amacrine cells in mammalian retinae

A distinct population of wide-field, unistratified amacrine cells are shown to be selectively stained by using neurofibrillar methods in rabbit and cat retinae. Their cell bodies may be located in the inner nuclear, inner plexiform or ganglion cell layers and they branch predominantly in stratum 2 of the inner plexiform layer. Characteristically, each cell has two or more long-range distal processes which extend for 2-3 mm beyond a more symmetrical, proximal dendritic field of 0.6-0.8 mm diameter. Although the neurofibrillar long-range amacrines account for less than 1 amacrine in 500, they achieve effective coverage of the retina by both the proximal and distal dendrites.     

Target cells of vitamin D in the vertebrate retina

Using PAP technique, cellular localization of vitamin D-dependent calcium-binding protein (D-CaBP) was investigated in vertebrate retina with monospecific antisera against chick duodenal D-CaBP. In the chick retina, the receptor cells were positive. In the inner nuclear layer, horizontal cells and some bipolar cells were also positive. Some amacrine cells as well as different levels of the inner plexiform layer were also positive for D-CaBP. A few interspersed ganglion cells were positive but their axons forming the optic tract were negative. Müller's cells were negative. In 1-day-old chicks and 4-week-old rachitic chicks there was paucity and absence, respectively, of D-CaBP staining in horizontal cells. In the mouse, rat, and rabbit the receptors had only trace amounts of reaction product in their outer segment and pedicle. Horizontal cells were densely positive throughout their cellular body and processes. Some amacrine cells in the inner nuclear layer were positive. In the mouse and rat three horizontal levels of the outer plexiform layer were very prominent because of their dense staining for D-CaBP. Many ganglion cells were also positive along with their axons forming the optic nerve. In the rabbit, no positive layers were seen in the inner plexiform layer, and ganglion cells with their fibers were negative. In the frog retina there were smaller amounts of D-CaBP in the receptor cells and horizontal cells than that of the chick retina. Also, the fibers of the ganglionic cells were positive for D-CaBP. In all species studied, some amacrine cells were stained for D-CaBP. Because of its possible roles in membrane calcium transport and intracellular Ca++ regulation, it has perhaps similar functions in these positive cells. The synthesis of D-CaBP is dependent upon vitamin D. These positive cells are thus target cells of vitamin D.     

THE DISTRIBUTION OF CHOLINE ACETYLTRANSFERASE ACTIVITY IN VERTEBRATE RETINA1

Abstract— Choline acetyltransferase (ChAc) activity was determined in retinal layers from 10 vertebrates. In all animals, the highest activity was in the inner plexiform layer, intermediate activity in the inner nuclear and ganglion cell layers, and very low activity in the photoreceptor and outer plexiform layers and optic nerve. The pattern of distribution of enzyme activity within the inner nuclear layer corresponds quantitatively to the distribution of amacrine cells within that layer. A species difference of almost 90-fold was found between the lowest and highest values for ChAc activity in inner plexiform layer. The variation in enzyme activity found among homeotherms in inner nuclear and inner plexiform layers is related to the number of amacrine cell synapses in the inner plexiform layer. But the differences in enzyme activity are generally greater than those which have been found in numbers of amacrine cell synapses between species. The data suggest that cholinergic neurons in retina are to be found predominantly among the amacrine cell types and that not all amacrine cells will be found to be cholinergic.     

Laminar Distributions of Choline Acetyltransferase and Acetylcholinesterase Activities in the Inner Plexiform Layer of Rat Retina

Choline acetyltransferase and acetylcholinesterase activities were measured in samples taken at 7-micron increments through the inner plexiform layer of rat retina. These enzyme activities were not uniformly distributed through the depth of the inner plexiform layer. Peaks of choline acetyltransferase activity occurred at about one-third and peaks of acetylcholinesterase activity at about one-fifth of the depth into the inner plexiform layer from either side. The positions of the two peaks of choline acetyltransferase activity most likely correspond to the locations of processes from cholinergic amacrine somata in the inner nuclear layer, which spread in sublamina a, and processes from cholinergic amacrine somata "displaced" in the ganglion cell layer which spread in sublamina b of the inner plexiform layer. The peaks of acetylcholinesterase activity may in addition correspond to the processes of cholinoceptive amacrine and ganglion cells. The magnitudes of choline acetyltransferase and acetylcholinesterase activities are as high as found anywhere in rat brain, emphasizing the important role of cholinergic mechanisms in visual processing through the rat inner plexiform layer.     

Light- and electron-microscopic study of substance P-immunoreactive neurons in the guinea pig retina

Substance P (SP) immunoreactivity in the guinea pig retina was studied by light and electron microscopy. The morphology and distribution of SP-immunoreactive neurons was defined by light microscopy. The SP-immunoreactive neurons formed one population of amacrine cells whose cell bodies were located in the proximal row of the inner nuclear layer. A single dendrite emerged from each soma and descended through the inner plexiform layer toward the ganglion cell layer. SP-immunoreactive processes ramified mainly in strata 4 and 5 of the inner plexiform layer. SP-immunoreactive amacrine cells were present at a higher density in the central region around the optic nerve head and at a lower density in the peripheral region of the retina. The synaptic connectivity of SP-immunoreactive amacrine cells was identified by electron microscopy. SP-labeled amacrine cell processes received synaptic inputs from other amacrine cell processes in all strata of the inner plexiform layer and from bipolar cell axon terminals in sublamina b of the same layer. The most frequent postsynaptic targets of SP-immunoreactive amacrine cells were the somata of ganglion cells and their dendrites in sublamina b of the inner plexiform layer. Amacrine cell processes were also postsynaptic to SP-immunoreactive neurons in this sublamina. No synaptic outputs onto the bipolar cells were observed.     

Serotonin-containing neurones in vertebrate retinas

Abstract: It has been established by a combination of HPLC and electrochemical detection that frog, lizard, goldfish, rabbit, and bovine retinas contain both dopamine and serotonin. Immunohistological and immunoradiographical methods show that serotonin is localised in amacrine perikarya and processes situated in the inner plexiform layers of frog, lizard, and goldfish retinas. The amount of serotonin in the mammalian retina appears to be too low for detection in neurones. The serotonin in the bovine retina is located mainly in the inner nuclear and plexiform layers, suggesting that the amine is present in the same types of cells as found for frog, lizard, and goldfish retinas. Retinas incubated in [³H]serotonin showed that radioactivity is associated with processes in the inner plexiform layer and amacrine perikarya. These results suggest that the neuronal elements that contain endogenous serotonin also have the capacity to accumulate exogenous amine and are consistent with the opinion that serotonin has a neuronal function in retinas of a variety of vertebrates.     

GABA neurones in retinas of different species and their postnatal development in situ and in culture in the rabbit retina

Summary The localisation of GABA immunoreactive neurones in retinas of a variety of animals was examined. Immunoreactivity was associated with specific populations of amacrine neurones in all species examined, viz. rat, rabbit, goldfish, frog, pigeon and guinea-pig. All species, with the exception of the frog, possessed immunoreactive perikarya in their retinal ganglion cell layers. These perikarya are probably displaced amacrine cells because GABA immunoreactivity was absent from the optic nerves and destruction of the rat optic nerve did not result in degeneration of these cells. GABA immunoreactivity was also associated with the outer plexiform layers of all the retinas studied; these processes are derived from GABA-positive horizontal cells in rat, rabbit, frog, pigeon and goldfish retinas, from bipolar-like cells in the frog, and probably from interplexiform cells in the guinea-pig retina.The development of GABA-positive neurones in the rabbit retina was also analysed. Immunoreactivity was clearly associated with subpopulations of amacrine and horizontal cells on the second postnatal day. The immunoreactivity at this stage is strong, and fairly well developed processes are apparent. The intensity of the immunoreactivity increases with development in the case of the amacrine cells. The immunoreactive neurones appear fully developed at about the 8th postnatal day, although the immunoreactivity in the inner plexiform layer becomes more dispersed as development proceeds. The immunoreactive horizontal cells become less apparent as development proceeds, but they can still be seen in the adult retina.The GABA immunoreactive cells in rabbit retinas can be maintained in culture. Cultures of retinal cells derived from 2-day-old animals can be maintained for up to 20 days and show the presence of GABA-positive cells at all stages. In one-day-old cultures the GABA immunoreactive cells lacked processes but within three days had clearly defined processes. After maintenance for 10 days a meshwork of GABA-positive fibres could also be seen in the cultures.     

Morphology of calretinin and tyrosine hydroxylase-immunoreactive neurons in the pig retina

The morphology of calretinin- and tyrosine hydroxylase-immunoreactive (IR) neurons in adult pig retina was studied. These neurons were identified using antibody immunocytochemistry. Calretinin immunoreactivity was found in numerous cell bodies in the ganglion cell layer. Large ganglion cells, however, were not labeled. In the inner nuclear layer, the regular distribution of calretinin-IR neurons, the inner marginal location of their cell bodies in the inner nuclear layer, and the distinctive bilaminar morphologies of their dendritic arbors in the inner plexiform layer suggested that these calretinin-IR cells were AII amacrine cells. Calretinin immunoreactivity was observed in both A-and B-type horizontal cells. Neurons in the photoreceptor cell layer were not labeled by this antibody. The great majority of tyrosine hydroxylase-IR neurons were located at the innermost border of the inner nuclear layer (conventional amacrines). The processes were monostratified and ran laterally within layer 1 of the inner plexiform layer. Some of the tyrosine hydroxylase-IR neurons were located in the ganglion cell layer (displaced amacrines). The processes of displaced tyrosine hydroxylase-IR amacrine cells were also located within layer 1 of the inner plexiform layer. Some processes of a few neurons were located in the outer plexiform layer. A very low density of neurons had additional bands of tyrosine hydroxylase-IR processes in the middle and deep layers of the inner plexiform layer. The processes of tyrosine hydroxylase-IR neurons extended radially over a wide area and formed large, moderately branched dendritic fields. These processes occasionally had varicosities and formed "dendritic rings". These results indicate that calretinin- and tyrosine hydroxylase-IR neurons represent specific neuronal cell types in the pig retina.     

Autoradiographic Localization of <Superscript>3</Superscript>H-GABA in Rat Retina

γ-AMINOBUTYRIC acid (GABA) is present in all layers of vertebrate retinae^1–3: in the rabbit retina it seems to be most concentrated in the ganglion cell layers² while in the frog it is concentrated primarily in cell layers which are rich in amacrine cells¹. Recent autoradiographic studies of the distribution of ³H-GABA in rat brain slices after incubation in vitro suggest that the labelled amino-acid is selectively concentrated by certain neural elements^4,5. In a study of the distribution of ³H-GABA in rabbit retina after injection of the labelled amino-acid into the eye, Ehinger⁶ found that radioactivity was accumulated principally in the inner plexiform, inner nuclear and ganglion cell and nerve fibre layers. Labelling was also concentrated in some cells occupying the same position as amacrine cells and in some nerve cells of the ganglion cell layer.     

Electron microscopic observation of pituitary adenylate cyclase-activating polypeptide (PACAP)-containing neurons in the rat retina

The distribution and localization of pituitary adenylate cyclase-activating polypeptide (PACAP) in the rat retina were studied by immunocytochemistry with both light and electron microscopy. PACAP-like immunoreactivity (PACAP-LI) was detected in the amacrine and horizontal cells as well as in the inner plexiform layer, the ganglion cell layer and the nerve fiber layer. PACAP-LI seemed to be concentrated predominantly in the neuronal perikarya and their processes, but not in other cells in the retina. At the ultrastructural level, PACAP-LI was visible in the plasma membranes, rough endoplasmic reticulum, and cytoplasmic matrix in the PACAP-positive neurons in the inner nuclear layer. In the inner plexiform layer, PACAP-positive amacrine cell processes made synaptic contact with immunonegative amacrine cell processes, bipolar cell processes, and ganglion cell terminals. These findings suggest that PACAP may function as a neurotransmitter and/or neuromodulator.     

VIP (Vasoactive Intestinal Polypeptide)-immunoreactive neurons in the retina of the rat

Summary Immunoreactive vasoactive intestinal polypeptide (VIP) was detected in a population of amacrine cells in the retina of the rat. Processes of these cells reach both the inner and outer half of the inner plexiform layer where they form sublayers. The VIP neurons are different from previously known amacrine cell types.     

A model for the mechanisms of sensitivity control in the submammalian vertebrate retina

A model is proposed for the mechanisms of sensitivity control at the outer and inner plexiform layers in the submammalian vertebrate retina on the basis of Werblin's results and other physiological results. The model is especially based on the following suggestions: The signal that acts to shift the bipolar curves is probably carried by horizontal cell processes extending from the surround to the center of the receptive field. Furthermore, amacrine cells carry a lateral antagonistic signal across the inner plexiform layer that affects the response properties of ganglion cells. The simulations of the model were made and the results of the ones considerably coincided with the experimental results of Werblin.     

Localization of CD15 immunoreactivity in the rat retina

Using immunocytochemistry, we have investigated the localization of CD15 in the rat retina. In the present study, two types of amacrine cell in the inner nuclear layer (INL) and some cells in the ganglion cell layer were labeled with anti-CD15 antisera. Type 1 amacrine cells have large somata located in the INL, with long and branched processes ramifying mainly in stratum 3 of the inner plexiform layer (IPL). Type 2 cells have a smaller soma and processes branching in stratum 1 of the IPL. A third population showing CD15 immunoreactivity was a class of displaced amacrine cells in the ganglion cell layer. The densities of type 1 and type 2 amacrine cells were 166/mm(2) and 190/mm(2) in the central retina, respectively. The density of displaced amacrine cells was 195/mm(2). Colocalization experiments demonstrated that these CD15-immunoreactive cells exhibit gamma-aminobutyric acid and neuronal nitric oxide synthase (nNOS) immunoreactivities. Thus, the same cells of the rat retina are labeled by anti-CD15 and anti-nNOS antisera and these cells constitute a subpopulation of GABAergic amacrine cells.     

Light-and electron-microscopic studies of the somatostatin-immunoreactive plexus in the cat retina

Summary Two monoclonal antibodies directed against somatostatin 14 were used to study immunoreactive neurons, their processes and their synapses in the cat retina. In retinal whole-mounts, a sparse population of wide-field displaced amacrine cells was observed predominantly in the ventral retina and near the retinal margin. Processes of these cells ramified mainly in two distinct strata within the inner plexiform layer: one near the inner nuclear layer (INL), and the other near the ganglion cell layer (GCL). The length of immunoreactive fibres within each plexus was measured: 232±32 mm/mm² near the INL and 230±74 mm/mm² near the GCL in all retinal regions. The immunoreactive processes were studied using electron-microscopic techniques; conventional and some ribbon-containing synapses (dyads) were found. Immunolabelled processes received input synapses from other amacrine cell processes. These investigations provide further evidence that this cell population has a diffuse, regulatory or modulatory role for visual-information processing in the inner plexiform layer.     

Distribution of calcitonin gene-related peptide immunoreactivity in the central nervous system of the forg,Rana esculenta

Summary Tyrosine hydroxylase (TH) immunocytochemistry was utilized to quantify dopaminergic synapses in the inner plexiform layer of the retina of Bufo marinus. Since dopaminergic cells have bistratified dendritic arborisation in the inner plexiform layer, attention was given to the segregation of synapses between the scleral and the vitreal sublaminae. Light-microscopically, a more elaborate dendritic branching was observed in the scleral than in the vitreal sublamina. In contrast, about 55% of synapses occurred in the vitreal one fifth of the inner plexiform layer, 30% in the scleral fifth, and 15% in the intermediate laminae. Input sources and output targets showed only minor quantitative differences between sublaminae 1 and 5. TH-immunoreactive processes were found in presynaptic (62.8%) and postsynaptic (37.2%) positions. Synapses to the stained dendrites derived from bipolar (40.4%) and amacrine (59.6%) cells, whereas outputs from the TH-positive processes were directed to amacrine cells (56.8%) and to small and medium-sized dendrites (35.4%); at least some of these can be considered as ganglion cell dendrites. TH-positive profiles neither formed synapses with each other nor were presynaptic to bipolar cell terminals. Junctional appositions of the immunoreactive profiles were occasionally seen on non-stained amacrine and ganglion cell dendrites in the scleral sublamina of the inner plexiform layer and on optic axons in the optic fibre layer. Although dopaminergic cells are mainly involved in amacrine-amacrine interactions, inputs from bipolar terminals and outputs to ganglion cell dendrites were also substantial, suggestive of a role also in vertical information processing.     

Fine structure of the retina of black bass, Micropterus salmoides (Centrarchidae, Teleostei).

The structure of light- and dark-adapted retina of the black bass, Micropterus salmoides has been studied by light and electron microscopy. This retina lacks blood vessels at all levels. The optic fiber layer is divided into fascicles by the processes of Müller cells and the ganglion cell layer is represented by a single row of voluminous cells. The inner nuclear layer consists of two layers of horizontal cells and bipolar, amacrine and interplexiform cells. In the outer plexiform layer we observed the synaptic terminals of photoreceptor cells, rod spherules and cone pedicles and terminal processes of bipolar and horizontal cells. The spherules have a single synaptic ribbon and the pedicles possess multiple synaptic ribbons. Morphologically, we have identified three types of photoreceptors: rods, single cones and equal double cones which undergo retinomotor movements in response to changes in light conditions. The cones are arranged in a square mosaic whereas the rods are dispersed between the cones.