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Biomedical subjects

B Ehinger

Publications and source records attributed to B Ehinger.

At least 127 records · Page 7Linked to original sources
PubMed1982

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.

Animals↗
PubMed1982

(3H)-muscimol, (3H)-nipecotic acid and (3H)-isoguvacine as autoradiographic markers for GABA neurotransmission.

Retinas from rabbit, goldfish and guinea-pig were exposed to (3H) GABA, (3H)-nipecotic acid and (3H)-isoguvacine either by intravitreal injection in vivo or by incubations in a balanced salt solution and the distribution of radioactivity was then studied with autoradiography. All substances labelled a similar set of presumed amacrine cells. Incubating at 0 degrees C, in 10-(5)M ouabain, or in 10-(3)M GABA inhibited the labelling by (3H)-muscimol whereas bicuculline (10-(4)M), and glycine (10-(3)M) were less efficient blockers. The result is interpreted as a neuronal uptake of (3H)-muscimol rather than as a GABA receptor binding. All the substances except (3H)-isoguvacine also labelled glia to such a degree that neuronal labelling was often disguised in rabbits and goldfish. Glial labelling by muscimol was less pronounced in guinea-pig. (3H)-isoguvacine (tested only in rabbits) gave a strong labelling of cells with the distribution of GABA neurons and only little glial labelling.

Animals↗
PubMed1982

Autoradiography of (3H)-5-hydroxytryptamine uptake in the retina of some mammals.

The uptake of indoleamines into the retina of rats, rabbits, cows, pigs, baboons. Cynomolgus monkeys, and man was studied by fluorescence microscopy and autoradiography. Indoleamines were either injected intravitreally or the retinas were incubated with them. Fluorescence microscopy failed to show any indoleamine accumulating neurons in all species investigated except rabbit, confirming previous observations. However, autoradiography showed uptake in a distinct class of neurons in cows and pigs. These neurons had their cell bodies among the amacrine cells and most of their processes branched in the middle of the inner plexiform layer. This is in contradistinction to the dopaminergic neurons, which in cows and pigs have all their processes in the outermost sublamina of the inner plexiform layer. The fluorescence microscopy is quite sensitive to small variations in the indoleamine molecule. The discrepancy between the results with fluorescence microscopy and autoradiography therefore suggest that there is an active uptake mechanism for indoleamines in cows and pigs but that the substances are rapidly transformed to compounds not possible to detect in the fluorescence microscope. No specific indoleamine accumulating mechanism was detected in the retina of rats, baboons, cynomolgus monkeys, or man.

Animals↗
PubMed1981

Cells accumulating 3h-glycine in the goldfish retina.

Glycine accumulating neurons occur among amacrine cells of the goldfish retina with processes distributed in the inner plexiform layer. Similar cells also occur, although much more rarely, among the horizontal cells and in the outer plexiform layer. The latter cells are readily observable only after heavy labelling. They may emit processes ending close to the photoreceptor terminals.

Animals↗
PubMed1980

Fluorescence and electron microscopical observations on the amine-accumulating neurons of the cebus monkey retina.

The organization of the Cebus monkey regina was analysed after the intraocular injection of 5,6-dihydroxytryptamine. This amine was taken up not only by the previously known dopaminergic neurons, but also by a set of indoleamine-accumulating neurons, whose processes are confined to the inner plexiform layer. The synaptic contacts of the dopaminergic neurons were analysed in the electron microscope after the processes of the indoleamine-accumulating neurons were destroyed by the intravitreal injection of the neurotoxic indoleamine, 5,7-dihydroxytryptamine. The subsequent injection of 5,6-dihydroxytryptamine induces certain changes in the dopaminergic neurons which accumulate the substance: electron-dense cores appear in the synaptic vesicles, and increased electron-density of mitochodrial and cellular membranes is often observed. The dopaminergic neurons were found to be presynaptic to amacrine cell perikarya and processes in the inner plexiform layer. In the outer plexiform layer they were presynaptic to both bipolar and horizontal cells, but they did not contact photoreceptors. The dopaminergic neurons received synapses only in the inner plexiform layer, from amacrine cell processes. It is inferred that in Cebus most dopaminergic neurons belong to a special class of retinal neuron, the interplexiform cells, which appear to transmit information centrifugally within the retina, from the inner to the outer plexiform layers. There are considerable similarities between the synaptology of the dopaminergic interplexiform neurons in the Cebus monkey and the goldfish retina, and the function of interplexiform neurons may therefore be similar in these two species.

5,6-Dihydroxytryptamine↗
PubMed1980

Monoaminergic neurons of the mudpuppy retina.

The mudpuppy retina was investigated with the histofluorescence method of Falck and Hillarp in normal animals and in animals injected intraocularly with alpha-methylnoradrenaline, 5,6-dihydroxytryptamine, or a combination of the two drugs. Catecholaminergic amacrine cells were found to form a thin layer of terminals at the border between the inner nuclear and the inner plexiform layers. Catecholaminergic interplexiform cells were not found. Indoleamine-accumulating amacrine cells were also observed. They are fifteen to twenty times more numerous than the catecholaminergic cells, and their terminals occur diffusely throughout the inner plexiform layer. In a number of eyes the majority of the indoleamine-accumulating terminals were eliminated with intraocular injections of the neurotoxin, 5,7-dihydroxytryptamine, but the reproducibility of this effect was not consistent. Intravitreal injections of 5,6 dihydroxytryptamine were used to label both types of neurons for electron microscopy. They were found to make conventional type synapses on amacrine cells and, less frequently, on bipolar cells.

5,6-Dihydroxytryptamine↗
PubMed1980

[3H]-dopamine release from the rabbit retina.

[3H]-Dopamine was found to be released from the rabbit retina in vitro by light stimulation, by 40 mM K+, and by alpha-MSH (alpha-Melanocyte-Stimulating Hormone) down to about 10(-7) M. The effect of alpha-MSH was dose-dependent. A number of known and putative retinal neurotransmitters and agonists (GABA, muscimol, glutamic acid, kainic acid, glycine, and carbachol, all 10(-4) M) were without significant effect. The results show that it is unlikely that there are excitatory receptors on the retinal dopaminergic neurons to any of the conventional transmitters. Further, alpha-MSH seems of interest as a possible neuroactive retinal substance, which was previously not been suspected.

Animals↗
PubMed1980

Vasoactive intestinal peptide nerves in ocular and orbital structures of the cat.

Vasoactive intestinal polypeptide (VIP), a neuronal peptide of ubiquitous occurrence in the body, is known to have strong vasodilatory effects and to promote secretion from many exocrine glands. Nerves displaying VIP immunoreactivity (VIP nerves) were detected in several orbital structures of the cat. Such nerves were numerous in the lacrimal glands and somewhat less numerous in the Harderian glands and the tarsal glands. The nerves surrounded glandular acini and small blood vessels. Intraocularly, VIP nerves were seen in the ciliary processes, in the posterior third of the ciliary muscle, and around small to medium-sized blood vessels in the posterior uvea. VIP nerve fibers were absent from vessels in the anterior uvea. This distribution may explain why intracranial stimulation in the oculomotor nerve exit region dilates the vessels of the choroid but not those of the iris. A large number of VIP-immunoreactive nerve cell bodies were observed in the pterygopalatine ganglion. Extirpation of this ganglion resulted in the disappearance of VIP nerves from the intraocular structures and from the lacrimal and Harderian glands. Removal of the superior cervical ganglion and the ciliary ganglion did not affect the VIP nerve supply. The results suggest that the VIP nerves originate in the pterygopalatine ganglion.

Animals↗
PubMed1979

Electron microscopy of the indoleamine-accumulating neurons in the retina of the rabbit.

The recently discovered indoleamine-accumulating retinal neurons were studied electron microscopically after destruction of the dopaminergic retinal neurons and subsequent labeling with 5,6-dihydroxytryptamine. These observations confirm earlier fluorescence microscopical studies on the distribution of the indoleamine-accumulating neurons in the rabbit retina. Their perikarya are known to be located in the inner nuclear layer (INL) among the amacrine cell bodies. Their processes are found only in the inner plexiform layer (IPL), most of them in the innermost third part of that layer. The indoleamine-accumulating terminals are pre- and postsynaptic to bipolar neurons in the innermost sublayer of the IPL. Reciprocal synapses are probably the rule. The synaptic vesicles of indoleamine-accumulating synapses onto bipolar cells are arranged in "globular" clusters around a central electron dense, round body. A number of synapses formed by unlabeled amacrine neurons with postsynaptic indoleamine-accumulating elements were also detected. These synapses were mainly found in the outermost third of the IPL. Synaptic contacts between presynaptic indoleamine-accumulating neurons and postsynaptic unlabeled processes of amacrine cells are very rare.

5,6-Dihydroxytryptamine↗
PubMed1979

Absence of indoleamine-accumulating neurons in the retina of humans and cynomolgus monkeys.

Indoleamine-accumulating neurons have previously been detected in cats, rabbits, goldfish, chicken, pigeons, and Cebus monkeys, and were therefore also looked for in humans and in Old World monkey. Cynomolgus irus. The monkey eyes were injected intravitreally with 50 microgram 5,6-dihydroxytryptamine, 5 microgram alpha-methylnoradrenaline, or both drugs simultaneously. The human retinas were incubated in either drug. Previous observations on the distribution of dopaminergic neurons were confirmed in the two species, but no indoleamine-accumulating neurons were detected. The result emphasizes the similarity between human and Old World monkey retinas and contrasts them with the retina of the New World monkeys.

5,6-Dihydroxytryptamine↗