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B D Drujan

Publications and source records attributed to B D Drujan.

At least 19 recordsLinked to original sources
PubMed1991

Possible neurotransmitter role of noradrenaline in the teleost retina.

The role of dopamine as a neurotransmitter in the retina of different species has been clearly established; however, there is still some controversy as to whether noradrenaline (NA) is present as a neurotransmitter in this tissue. In this study, we show that, under controlled conditions, NA is present in the retina of goldfish at a concentration of 0.15 +/- 0.03 ng/mg protein and its biosynthetic enzyme, dopamine beta-hydroxylase shows an activity of 2.5 +/- 0.2 pmol NA/hr/mg protein. The amount of NA increases to 1.88 +/- 0.24 ng/mg protein in light adapted animals and decreases to undetectable levels in dark adapted ones. By contrast, dopamine-beta-hydroxylase levels are not affected by changes in light conditions. This finding provides further evidence in favor of a neurotransmitter role for NA in vertebrate retina.

Adaptation, Physiological↗
PubMed1990

Retinal neurotransmitter interaction as reflected in horizontal cell spatial behaviour.

The effects of 5-hydroxytryptamine (5-HT) and its precursors 5-hydroxytryptophan (5-HTP) and L-tryptophan (L-Tryp) on the spatial properties of horizontal cells were studied in the isolated and perfused retina of the teleost Eugerres plumieri. All three compounds produce a contraction of the receptive field, evaluated by the ratio of responses evoked by local and distant light stimuli. This is the result of cell uncoupling, revealed by the hindrance to diffusion of intracellularly injected Lucifer yellow. Similar effects are produced by dopamine (DA) and the effectiveness is DA much greater than 5-HT greater than 5-HTP greater than L-Tryp. All these effects are blocked by Haloperidol. HPLC studies of endogenous DA release reveal that it occurs when isolated retinas are incubated with 50 mM potassium, 10 microM 5-HT or 5-HTP, but is not found with up to 1 mM L-Tryp. The results indicate that indolaminergic cells induce the release of DA from interplexiform cells, which in turn uncouples horizontal cells in the fish retina.

5-Hydroxytryptophan↗
PubMed1988

Identification of horizontal cells generating different spectral responses in the retina of a teleost fish (Eugerres plumieri).

Six different types of spectral responses were recorded from horizontal cells under mesopic conditions in perfused retina, isolated from the dark-adapted mojarra (Eugerres plumieri). They were tentatively termed photopic Lr-, Lg1-, Lg2-, Lb-, and C-type, and scotopic L-type. The Lr-, Lg-, and Lb-type responses showed a maximum peak at 605, 550, and 516 nm respectively, while the C-type was composed of hyperpolarizing potentials in response to shorter wavelengths and depolarizing potentials in response to longer wavelengths (so-called R/G-type). The scotopic L-type has a peak at 516 nm in the spectral response and a slow decay phase in the waveform response. Following a brief period of diffuse illumination, it was found that the Lg1-type response is altered to the Lr-type, while both Lg2- and Lb-type responses change to the C-type. Intracellular marking with Lucifer or Procion yellow identified the cellular origins of different response types: external (He) and medial horizontal (Hm) cells for the Lr-type, internal horizontal (Hi) cells for the C-type, and rod-horizontal (Hr) cells for the scotopic L-type. Only He cells were found to possess an axon, while dye coupling was seen between axonless Hm, Hi, or Hr cells but not between He cells. The morphology of these fluorescent dye-marked cells was the same as that of the respective cells observed in Golgi-stained materials.

Animals↗
PubMed1987

Dopamine and noradrenaline content in fish retina: modulation by serotonin.

The presence of noradrenaline (NA) and the possible interaction of serotonin (5-HT) with dopaminergic and noradrenergic neuronal elements was studied in the retina of the teleost Eugerres plumieri. By means of a histofluorescent technique, paired amacrine cells can be visualized after intravitreal injection of NA or 5,6-dihydroxytriptamine, suggesting their probable catecholaminergic and indoleaminergic nature. With a high-performance liquid chromatographic (HPLC) method and after pargyline treatment of the animal, 6.86 ng/mg protein of dopamine (DA) was detected, while NA content was 0.50 ng/mg protein. The NA levels of the retina increased, whereas the DA levels decreased in a significant manner after in vivo treatment with 5-HT. 5-methoxy-N,N-dimethyltryptamine, a 5-HT agonist, was able to mimic this effect partially, while the agonists tryptamine and quipazine did not affect the levels of DA and NA. The antagonists methysergide, metergoline, and cyproheptadine significantly blocked the 5-HT-induced NA increase, whereas only the first two antagonists were effective in inhibiting the 5-HT-induced DA decrease. The 5-HT modulation of NA and DA is apparently receptor mediated and is not due to a hetero-exchange, since imipramine was not able to block the 5-HT effect. These findings support the suggested interaction between serotoninergic and dopaminergic cells [Negishi et al: J Neurosci Res 5:621-635, 1980; Neurosci Lett 25:1-5, 1981]. Furthermore, they demonstrate the possible modulation which 5-HT exerts on the endogenous levels of NA.

Animals↗
PubMed1984

Taurine- and penicillin-induced epileptic activity.

The present study has been performed to investigate the effect of i.v. administration of taurine on the electrical activity of the epileptogenic focus induced by penicillin applied to the right sensory motor cortex of adult rats. Taurine (100 mg/kg body weight) was administered 15, 30, 60, and 120 min before the application of penicillin. The EEG was unipolarly recorded by means of electrodes applied to the pia. Taurine caused a decrease of the frequency as well as the spike amplitude of epileptic discharge. The spread of epileptogenic foci to the opposite hemisphere was retarded when compared to that of control animals. The maximal antiepileptic effect of taurine was observed when the amino acid was administered 30-60 min previous to penicillin. It is suggested that high concentrations of taurine in the brain might be necessary to inhibit the epileptic activity.

Animals↗
PubMed1980

Drug-induced changes in catecholaminergic cells of the fish retina.

The changes in fluorescence intensity and number of visible catecholaminergic cells (CA-cells), as revealed by means of a histofluorescence technique, were used as indicators of the effects of various pharmacological agents upon CA-cells in the retina of fishes (Cyprinus carpio and Eugerres plumieri). The study includes in vivo and in vitro experiments. In the in vivo experiments, intravitreal injection, two or three hours before eye enucleation, of 10 microgram L-DOPA, dopamine, or noradrenaline accentuated CA-cell fluorescence and increased the number of visible cells, whereas 10 microgram of tyramine, octopamine, synephrine, or adrenaline reduced the endogenous fluorescence. Intramuscular injection of reserpine (3 mg/kg) abolished CA-cell fluorescence. In the in vitro experiments, pieces of isolated retinas were incubated for three or 30 minutes in media containing different drugs. Only minor changes in fluorescence were detected after three minutes of incubation, but after 30 minutes, dopamine (20 microM) markedly enhanced CA-cell fluorescence. Carbachol (20 mM), acetylcholine (10 mM) plus BW-anticholinesterase (1 mM) or substance P(1.6 x 10(-2) mM), all reduced CA-cell fluorescence. Kainic acid (20 mM) abolished fluorescence from CA-cell somata, while fluorescent fiber networks remain unchanged. L-aspartate (5 mM) and GABA (10 mM) in the incubation medium did not influence fluorescence intensity. The results are relevant to, and consistent with, electrophysiological observations of dopamine-mediated spatial effects on horizontal cell potentials.

Acetylcholine↗
PubMed1980

Spatial distribution of catecholaminergic cells in the fish retina.

The cell density, distribution pattern, and morphology of catecholaminergic (CA) cells have been studied by fluorescence microscopy of retinal flat-mounted preparations from various species of fresh water, estuary, and marine is lowest in the central region surrounding the optic disc, slightly higher in the intermediate region, and highest in the periphery. The size of CA-cells is smaller the higher their density. Following administration of L-Dopa, dompamine, or noradrenaline, the density of CA-cells approximately doubled, due to the appearance of small fluorescent cells. CA-cells are arranged in rows along radial lines which fan out from the optic disc. In large cells of the central and intermediate regions three to five processes arise from the some and extend and ramify irregularly in the inner plexiform layer, while in small cells from the intermediate and peripheral regions two processes arise from opposite poles and extend regularly in a direction perpendicular to the rows of cells and parallel to the retinal margin. In the retina of the marine fish Holocentrus sp CA-cells are fewer in number compared to other fish studied and their processes extend without any regular pattern. In the toad their size and density are homogenous throughout the retina, and their processes show a regular arrangement.

Animals↗
PubMed1979

Effects of catecholamines and related compounds on horizontal cells in the fish retina.

The effects of catecholamines (CA) and certain related compounds in the superfusate were examined on the intracellularly recorded potential from horizontal cells in the fish (Eugerres plumieri) retina. The stimulated retinal area consisted of a central spot 1.0 mm in diameter and an annulus 2.0 mm in inner diameter and 4.0 mm in outer diameter; both forms of monochromatic stimuli were centered relative to the recording microelectrode. Each of the CA (dopamine, noradrenaline, and adrenaline) produced an analogous effect on the hyperpolarizing response of all types of horizontal cells. The depolarizing response of the C (R/G)-type cells was found to change variably with the CA. The effect of dopamine (DA) among the CA was most pronounced when they were used at an equivalent amount. With 10--50 microM, the action of DA was variable but in general its effect was to increase slightly both center and surround responses. In some cases, however, DA initially augmented the surround and reduced the center response. Large amounts of the CA (100--200 microM) augmented the center response and attenuated the surround response considerably; these reciprocal changes usually were associated with moderate depolarization of the cells (5--10 mV). Recovery then occurred in 15--20 minutes. These results indicate that the CA, up to a certain amount, do not directly affect the transmission from photoreceptors to horizontal cells, since the center response became larger. At the same time, the lateral propagation of an S-potential appears to be selectively affected by the CA, suggesting that the adrenergic system participates in this phenomenon. When an excess of these compounds (200-500 microM) was given, the cells were rapidly depolarized to near 0 MV and eventually the light-induced responses were abolished. Large amounts (5--10 mM) of metabolic products of the CA (DOPAC and VMA) were found to reduce the center response slightly more than the surround. alpha-Methylnoradrenaline, 5-hydroxydopamine, and serotonin also caused the same but less effect on horizontal cells as did DA. Reserpine and clonidine mimicked the CA effect only if these compounds had been preceded by repeated applications of one of the CA or if the retina had been pretreated with Marplan. Propranolol, haloperidol, and apomorphine affected neither the horizontal cell membrane potential nor the CA effect. However, phentolamine in large amounts (500 microM) markedly diminished the DA action. Therefore, alpha-adrenergic receptors appear to be involved in the CA-induced changes observed in the horizontal cell response.

3,4-Dihydroxyphenylacetic Acid↗
PubMed1979

Similarities in effects of acetylcholine and dopamine on horizontal cells in the fish retina.

The effect of acetylcholine (ACh) on cone- and rod-connected horizontal cells (generating photopic and scotopic L-type S-potentials, respectively) in the fish (Eugerres plumieri) retina was compared with that of dopamine (DA), and some similarities were found in the effects. About two-thirds of the L-type horizontal cells examined were sensitive to a test solution containing ACh (10 mM in concentration) and BW-anticholinesterase (BW; 1.0 mM). ACh with BW augmented a center response and attenuated a surround response as did DA (0.2 mM), although the latter effect was more pronounced and longer-lasting. ACh with BW frequently produced oscillations of the horizontal cell membrane potential, as did DA with clonidine (alpha-adrenergic stimulant). Phentolamine (alpha-adrenergic blocker) interrupted both the effects of DA and ACh on the center and surround responses, while hexamethonium (cholinergic antagonist) appeared to interfere selectively with the effect of ACh. Therefore, the ACh-induced changes observed in the horizontal cell membrane potential are assumed to be mediated by the adrenergic system in the fish retina.

Acetylcholine↗
PubMed1979

Effects of some amino acids on horizontal cells in the fish retina.

Effects of some amino acids on horizontal cells were examined in the fish (Eugerres plumieri) retina. L-aspartate (5 mM in concentration) and L-glutamate (10 mM) consistently depolarized all types of horizontal cells, although the effect of L-aspartate was more pronounced. gamma-Aminobutyric acid (GABA; 10 mM) consistently hyperpolarized the cone-connected L- and C-type horizontal cells, whereas the effect on the rod-connected cells was slight or nonexistent. The hyperpolarizing effect of GABA on the cone-horizontal cells was markedly diminished by picrotoxin (0.1 mM). Usually, glycine (10 mM) showed slight and variable effects. It merely depolarized some cone-horizontal cells but weakly hyperpolarized some rod-horizontal cells. In a few cases, however, glycine began to drastically hyperpolarize the cone-horizontal cells in retinas that had been repeatedly treated with certain agents used. Taurine and beta-alanine (10 mM each) had negligible effects, although the former slightly depolarized and the latter merely hyperpolarized both cone- and rod-horizontal cells.

Amino Acids↗
PubMed1979

Reciprocal changes in center and surrounding S potentials of fish retina in response to dopamine.

Effects of dopamine (DA) were examined on the intracellularly recorded potential from horizontal cells in the fish (Eugerres plumieri) rentina. DA (100 micron in the perfusate) augmented the center S potential in a response to a spot illumination and attenuated the surrounding S potential to an annular light by approximately 40%. These reciprocal changes in the S potentials were associated with a slight depolarization (2.5 mV) of the horizontal cell, and were reversible in 10-15 min. The results indicate that DA at this concentration does not affect directly the synaptic transmission from photoreceptors to horizontal cells, while it appears to interfere selectively with the lateral propagation of an S potential. The effects of DA observed may represent an aspect of function of DA-containing interplexiform cells in the retina.

Animals↗
PubMed1979

Histochemical studies on catecholaminergic cells in the carp retina.

Histochemical studies on catecholaminergic cells were conducted with the carp (Cyprinus carpio) retina. Catecholamine (CA)-containing cell bodies appear sparsely distributed among amacrine cells in the innermost cellular row of the inner nuclear layer (INL) and occasionally in the outer half part of the inner plexiform layer (IPL); only exceptionally are they found among ganglion cells. The fluorescent cells interspersed with the amacrine cells and in the IPL send their fiber processes toward both the outer plexiform layer (OPL) and the IPL; the fine fibers form dense networks in the INL and IPL. Pretreatment of the fish with intramuscular injection of reserpine (20 hr prior to enucleation) completely depleted CA from the retina. The fluorescence of catecholaminergic cells was enhanced, and the number of fluorescent cells visible was increased, by intravitreous injection of L-DOPA, DA, and NA (3 prior to enucleation). A combination of pretreatment with intramuscular reserpine and intravitreous NA was particularly effective. These results indicate that catecholamines may play an important role in the modulation of the membrane potential of horizontal cells.

Animals↗
PubMed1979

Histochemical and cytochemical localization of acetylcholinesterase in retina and optic tectum of teleost fish.

The activity of cholinesterase and its cellular and subcellular localization were investigated in the retina and optic tectum of Eugerres plumieri and in the retina of Carassius carassius by means of radiometric, histochemical, and cytochemical procedures. In both fishes only the presence of acetylcholinesterase could be demonstrated. This study, besides confirming previous findings that acetylcholinesterase is located in the ganglion and amacrine cells of the retina as well as in the inner plexiform layer, in addition provides evidence that the enzyme is also present at the region of photoreceptor synapses between the cell bodies and apposing extensions of the horizontal cells of the same layer. The latter localization may indicate the involvement of a cholinergic mechanism at the functional contacts (transferapses) between the horizontal cells. In the optic tectum of Eugerres plumieri, histochemistry reveals fine distinguishable bands of acetylcholinesterase activity; two of the bands are quite sharply defined, whereas three others have rather a more diffuse appearance. The presence of these bands and their distribution may suggest a widespread distribution of cholinergic elements in the optic tectum.

Acetylcholinesterase↗
PubMed1978

Interrelated changes of amino acids in the retina and optic tectum of a marine fish with alterations of illuminating conditions.

Examination of interrelated changes in the concentrations of 'clusters' of amino acids provides evidence that individual amino acid levels in the tissues cannot be considered to vary independently. Such variations are observed when the CNS at 'rest' is stimulated. Alterations in taurine cause changes in glutamic acid and also modify its anatomically related compartmentalized metabolism. Similar interdependent modifications may be indicated for the concentrations of 3 biochemically related neutral amino acids: threonine, serine and glycine. With specific reference to the fish optic tectum and retina, certain differences and coincidences in the regulation of GABA and glycine have also been uncovered. Finally, many of the findings presented here are closely analogous to results obtained when comparing normal and epileptic mammalian tissues. Possibly, this analogy can be attributed to the fact that the physiological states so far investigated, from the most simplistic point of view, represent extreme variations of nervous tissue excitation.

Amino Acids↗
PubMed1978

Some properties of phenylethanolamine-N-methyltransferase of rat brain.

Phenylethanolamine-N-methyltransferase (PNMT, EC 2.1.1.28) was partially purified from rat brain. Brain homogenates were subjected to ultracentrifugation, salt fractionation, and gel filtration on Sephadex G-100. To compare the rat brain PNMT with that of adrenals, the same procedure was carried out with rat adrenal homogenates. The brain enzyme was eluted from Sephadex as a single fraction with a molecular weight of 26,900, while the enzyme from adrenals under the same conditions appeared in two fractions with molecular weights of 38,700 and 108,500. The brain fraction separated on Sephadex G-100 was active on phenylethanolamine substrates and inactive on indoleamine and phenylethylamine substrates. Products of the enzyme reaction were identified by bidimensional thin-layer chromatography as N-methyl derivatives of the corresponding amines. Kinetic studies showed that the type of inhibition of PNMT from rat brain and rat adrenals by SK&F 7698 was the same as described for PNMT from rabbit adrenals. Also, when normetanephrine and S-adenosyl-L-methionine were used as substrates, the apparent Km values found with PNMT from rat adrenals and rat brain were similar.

Adrenal Glands↗