Spatial density of catecholaminergic cells in the carp retina

New aspects of dopaminergic interplexiform cell organization in the goldfish retina

Dopaminergic interplexiform cells (DA-IPCs) in the goldfish retina have been reexamined by light and electron microscopic immunocytochemistry with antisera against dopamine (DA) or tyrosine hydroxylase (TH). Successful immunostaining with a specific anti-DA antiserum offers further direct support for DA-IPCs. Anti-DA immunocytochemistry in combination with [3H]-DA autoradiography shows 92% colocalization of the two markers, indicating that [3H]-DA autoradiography is a reliable technique for identification of DA-IPCs. Incubations with anti-TH antiserum show that immunoreactive DA-IPCs have a homogeneous distribution, with an average frequency of 71 +/- 8 cells/mm2 in retinas of 14-15 cm long goldfish. Their arrangement is distinctly nonrandom. Electron microscopy of TH-immunoreactive cell processes confirms that horizontal cell axons synapse onto DA-IPCs and adds the following junctional arrangements to the circuit diagram of the DA-IPC: 1) adjacent serial synapses between DA-IPCs, external horizontal cells, and putative glycinergic interplexiform cells, 2) junctional appositions between DA-IPCs and photoreceptor cells, 3) junctional appositions between neighbouring DA-IPCs, and 4) the "gap junctional complex," typically consisting of a DA-IPC process juxtaposed with a gap junction between horizontal cell axons. The gap junction is flanked by clusters of small, round vesicles and groups of electron-dense structures resembling intermediate filaments. These morphological results support the functional involvement of DA-IPCs in adaptive retinomotor movements and in horizontal cell gap junction modulation and/or dynamics. They also suggest particular interaction between the dopaminergic and the glycinergic IPC system in the outer plexiform layer of goldfish retina.

Age-dependent changes in fluorescent neurons in the brain of Notoplana acticola, a polyclad flatworm

The formaldehyde-glutaraldehyde-sucrose (FGS) method for in situ localization of catecholamines has been applied to the nervous system of the marine polyclad flatworm Notoplana acticola. This histochemical fluorescence technique revealed the presence of a small population of fluorescent cells within the brain. The number and positions of these neurons were constant in animals of the same size, but varied with the size of the worm. The brains of small animals (8 mm in length) were found to contain 20 fluorescent cells, whereas the largest animals studied (30 mm in length) were found to have 28 such cells. Various intermediate cell numbers were found in animals between these two sizes. The origin of the newly added fluorescent cells is uncertain. Peripheral fluorescence was found in association with the tentacular ocelli (eyespots) and interneurons within the ventral submuscular nerve plexus. The fluorescent spectrum from these cells measured in situ had a lambda max of 526 nm. Treatment with HCl shifts this peak to 530 nm. L-dopamine fluoresces with a similar peak emission before HCl treatment (525.5 nm) and shifts to the appropriate longer wavelength (530 nm) following acidification. This strongly suggests that the fluorescent substance in the neurons is dopaminergic in nature.

Cytological features of serotonin-containing neurons and their processes in the retina of the carp (Cyprinus carpio). An immunohistochemical study using flat-mount preparations

The morphological features of serotonin-containing neurons (SCNs) and their processes in the retina of the carp (Cyprinus carpio) were immunohistochemically studied by applying a modified peroxidase-antiperoxidase technique using flat-mount preparations. The somata of immunoreactive SCNs were mostly located in the innermost part of the inner nuclear layer (INL). These cells were distributed at a density of 64.8 cells/mm2, this being similar to the density of dopamine-containing interplexiform cells. The processes of the SCNs ramified successively into two finer branches, eventually forming a broad, extensive network in the thin layer just subjacent to the plane of the somata of the SCNs. Processes originating from neighboring SCNs exhibited cytoplasmatic continuity with each other at the lightmicroscope level. Due to their location and cytological features, these SCNs appeared to correspond to amacrine cells.

Morphology and distribution of tyrosine hydroxylase-like immunoreactive neurons in the cat retina

In cat retina, antisera directed against tyrosine hydroxylase (tyrosine 3-monooxygenase; EC 1.14.16.2) labeled three morphologically distinct classes of neurons; amacrine cells, displaced amacrine cells, and interplexiform cells. These three cell populations differed not only in their morphologies but also in their numbers, densities, and retinal distributions. Insofar as tyrosine hydroxylase-like immunoreactivity is associated with dopaminergic neurons, these observations suggest that the dopamine system in cat retina is morphologically heterogeneous and that the cat retina contains functional subdivisions based on the different distributions of specific cell populations.

Spatial distribution of visual pigment and dopamine in the bullfrog retina

Visual pigments and a neurotransmitter, dopamine, were quantitatively investigated in the retina of adult bullfrog, Rana catesbeiana. The adult bullfrog (body length 15-16 cm, body weight 375 +/- 52 g, n = 10) had 21.4 +/- 4.2 nmol visual pigment and 209 +/- 28 pmol dopamine in retinal areas of 266 +/- 27 mm2. Greater pigment densities were recorded in a semicircular band around the optic disc, extending to the nasal and temporal peripheries of the ventral retina. The area with the highest concentration of visual pigment was found in the middle of the dorsal retina, 3-4 mm dorsal to the optic disc. A high concentration of vitamin A2-based pigment was found in the dorsal quarter of the retina (porphyropsin zone); the zone extended up to the most ventral part along peripheral regions of the retina. There was also a band with higher dopamine concentrations although it was not so prominent as that of the visual pigment; the highest concentration of dopamine was found in the area immediately dorsotemporal to the optic disc. Fluorescence micrography indicated that the distribution pattern of catecholamine-containing amacrine cells paralleled that of the dopamine content. The topographic map of dopamine was slightly different from that of visual pigment in the bullfrog retina.

Responses of the pigmented rabbit retina to NMPTP, a chemical inducer of parkinsonism

The electrophysiological and neurochemical effects of N-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (NMPTP), a chemical inducer of Parkinsonism in man and monkeys, on the pigmented rabbit retina were determined under both chronic and acute conditions. The implicit time, the oscillatory potentials, and the amplitude of the b-wave of the rabbit electroretinogram were affected; both dopamine and dihydroxyphenylalanine (DOPA) levels were depressed. Ultrastructural analysis of acute and chronic retinas showed the occurrence of an intranuclear filamentous inclusion in the nucleus of some cells in the inner nuclear and ganglion cell layer of chronic samples. The effects of the neurotoxin NMPTP on the retina suggest that dopaminergic metabolism is impaired, which then affects the components of the electroretinogram attributed to both bipolar and amacrine cells. In addition, the retina may provide a model in which to study the bichemical and pharmacological mechanisms of NMPTP toxicity.

Dopamine-containing amacrine cells of rhesus monkey retina parallel rods in spatial distribution

Dopamine-containing amacrine cells of rhesus monkey were found everywhere outside of the foveola in whole, flat retinas by the formaldehyde-glutaraldehyde fluorescent method. There were about 7500 such cells in a single retina and their density, determined by cell counts and measured by a nearest neighbor method, was minimal in foveal and peripheral regions and maximal at 3 mm from the center of the fovea. Compared to density distributions of other retinal neuron types, dopamine-containing amacrine cells correlated only with rods, which also had a peak density at 3 mm eccentricity. Cones and ganglion cells peaked in the foveal pit, or within 1 mm of it, respectively. As the distribution of dopamine-containing cells followed that of rods, it is suggested that dopamine could be involved in the rod neuronal circuitry of primates.

Differentiation of monoamine accumulating neuron systems in cultured chick retina: an immunohistochemical and fluorescence histochemical study

Monoamine-containing neurons (dopamine and serotonin) have been reported to be localized among the cells in the inner nuclear layer (INL) of the chick retina. To examine the development of these neurons and whether they have an ability to synthesize serotonin (5-HT) or dopamine from exogenous precursors, we administered monoamines and their precursors in vitro as well as in situ and examined monoamine neuronal differentiation histochemically. In the chick retina, serotonin-containing neurons were found among amacrine cells. Two other types of serotonin-accumulating neurons were observed in the INL. One also had the ability to take up tryptophan and 5-hydroxytryptophan (5-HTP) and convert them to serotonin. In the monolayer culture from 61/2-day-old chick embryonic retinas, serotonin-containing neurons were observed on the 4th day of culture, increased in number until the 8th day, but had almost disappeared by the 15th day. After incubation of 8 day-cultures with 5-hydroxytryptophan, the number of serotonin-immunoreactive cells was at least twice that seen in untreated cultures. On the 20th day of culture, the same percentage of cells had the capability to take up serotonin, but the number of those which took up 5-hydroxytryptophan and decarboxylated it to serotonin had decreased markedly. Dopaminergic amacrine cells have also been found in the INL and shown to take up exogenously administered L-DOPA. In cultures, no dopamine-containing cells were observed with the present fluorescence histochemistry without prior incubation with DOPA.(ABSTRACT TRUNCATED AT 250 WORDS)

Spatial organization of neurochemically classified interneurons of the goldfish retina-I. Local patterns

Certain interneurons in the goldfish retina are uniquely specifiable by their abilities to take up exogenously supplied [3H]gamma-aminobutyric acid (GABA), [3H]glycine, [3H]dopamine of [3H]serotonin al low micromolar concentrations. Each ligand labels one or two unique populations of interneurons yielding six cell types characterized by soma location, soma size, level and form of dendritic arborization, and local spatial patterning. This report summarizes these qualitative features and provides quantitative evidence on the size and spatial distributions of : (1) GABA-ergic horizontal cells, (2) GABA-ergic amacrine cells, (3) glycinergic amacrine cells; (4) glycinergic interplexiform cells; (5) dopaminergic interplexiform cells; and (6) indoleaminergic amacrine cells.

Indoleamine-accumulating cells and dopaminergic cells are distributed similarly in carp retina

Carp (Cyprinus carpio) retinas were processed for simultaneous visualization of dopaminergic (DA) and indoleamine-accumulating (ID) cells in flat-mounts under fluorescence microscope. A mixture of 5 micrograms noradrenaline (NA) and 5 micrograms 5,6-dihydroxytryptamine (5,6-DHT) was injected intravitreally into the eyes 2 h before enucleation. The spatial distribution and density were compared between NA-loaded DA-cells (greenish fluorescence) and 5,6-DHT-loaded ID-cells (yellowish). The two classes of cells were found to distribute similarly in a mixed fashion. Their densities were higher in the peripheral region than in the rest and extremely high at the retinal margin. Where the densities were higher, the size of cell bodies tended to be smaller. DA-cells were generally larger than ID-cells. Those cells, located in the intermediate and peripheral regions, appeared to be arranged in radial rows originating at the optic disc.