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  • 1
    ISSN: 1435-1463
    Keywords: Avian pineal organ ; serotonin ; noradrenaline
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Résumé La répartition des monoamines endogènes a été examinée dans l'organe pineal de la Perruche adulte (Melopsittacus undulatus, Shaw), par la méthode de Falck et Hillarp. Les pinéales des Oiseaux, soumis à une photopériode naturelle et sacrifiés le matin, montrent: 1. une intense fluorescence jaune de l'épithélium épiphysaire, uniquement dans les photorécepteurs rudimentaires sécrétoires (PRS) au niveau de la partie proximale de leur segment interne, du cytoplasme périnucléaire et des pédicules basaux; 2. de rares fibres nerveuses à fluorescence verte qui parcourent les espaces périvasculaires bordant le tissu pinéalien. L'analyse microspectrofluorimétrique indique que: 3. la fluorescence jaune des PRS signale l'existence de sérotonine (5-hydroxytryptamine, 5-HT), bien que la présence de 5-hydroxytryptophanne ne puisse être exclue; 4. la noradrénaline est le neurotransmetteur normal des fibres nerveuses orthosympathiques. La déplétion des monoamines épiphysaires est obtenue après injection de réserpine. La quantité de 5-HT est plus ou moins réduite dans les PRS après inhibition des enzymes responsables de l'hydroxylation et de la décarboxylation. Les taux de 5-HT et de noradrénaline augmentent après action des inhibiteurs de la monoamine oxydase. Il est démontré que la 5-HT est stockée plus particulièrement, sinon exclusivement, dans les zones de grains denses de sécrétion (500–1200 Å) des photorécepteurs rudimentaires sécrétoires. Compte tenu des résultats de cette étude, des recherches cytophysiologiques effectuées pour l'épiphyse des Lacertiliens et des données biochimiques obtenues chez les Oiseaux, nous proposons que les voies de synthèse et du métabolisme de la 5-HT se situent dans les PRS. La localisation des indolamines endogènes correspond à celle des indolamines exogènes (Collin et al., 1976).
    Notes: Summary The distribution of endogenous monoamines was investigated in the pineal organ of adult parakeet (Melopsittacus undulatus, Shaw) using the Falck and Hillarp technique. Formaldehyde-treated pineal organs of birds, kept under natural photoperiodical conditions and autopsied in the morning, show: 1. an intense yellow fluorescence in the parenchyma, present only in the secretory rudimentary photoreceptor (SRP) cells at the level of the proximal part of the inner segment, perinuclear cytoplasm and basal processes; 2. scarce green-fluorescent nerve fibres which run in the perivascular spaces bordering the pineal tissue. The microspectrofluorimetric analysis indicates: 3. that the yellow SRP fluorophore is identical with serotonin (5-hydroxytryptamine. 5-HT), although the presence of 5-hydroxytryptophan cannot be excluded; 4. that noradrenaline is the normal neurotransmitter in the sympathetic nerve fibres. After the depleting activity of reserpine, pineal monoamines are absent. The amount of 5-HT is more or less decreased in SRP cells after inhibition of the hydroxylating and decarboxylating enzymes. 5-HT and noradrenaline levels are increased after monoamine-oxidase inhibitors. It is concluded that 5-HT, a precursor of melatonin, is stored in the regions in which dense secretory granules (500–1200 Å) are present in the SRP cells. As a result of this study and other cytophysiological investigations on the pineal of Lacertilians and biochemical findings in birds, it is proposed that pathways of synthesis and metabolism of 5-HT are located in SRP cells. The distribution of endogenous and exogenous (Collin et al., 1976) indoleamines is similar.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-1106
    Keywords: Avian pineal ; SRP cells ; Serotonin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The uptake of 5-hydroxytryptophan (3H-5-HTP) and serotonin (3H-5-HT) and their distribution have been demonstrated, at the ultrastructural level, in the secretory rudimentary photoreceptor cells (SRP cells), in the pineal organ of the parakeet and the duck. In vivo experiments. When the parakeets were injected with 3H-5-HTP alone or pretreated with drugs interfering with monoamine metabolism (e.g. R04-4602, nialamide) prior to injection of the label, the SRP cells always exhibited specific radioautographic reactions, in the regions of the dense secretory granules of the cell body and asynaptic pedicles. The labeling concentration varied quantitatively with time (interval between injection of the label and sacrifice) and drugs used. In vitro experiments. The uptake of 3H-5-HTP and 3H-5-HT in the pineal organ of the duck has also been studied, using an incubation procedure. The results with the two precursors confirmed those obtained “in vivo” with the parakeet. From these results it is suggested that the uptake of precursors in some compartments of SRP cells is qualitatively independent of: a) the experimental period (experiments performed in winter, spring, and summer; uptake of precursors between 11.00 a.m. and 12.00) b) the precursor (3H-5-HTP or 3H-5-HT) c) the observation times. It is concluded that the SRP cell, an important step in the cytological and functional evolution of the pineal organ (Collin, 1969, 1971), is responsible for the synthesis of 5-HT. The metabolism of 5-HT seems also possible in such cells.
    Type of Medium: Electronic Resource
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