The avian pineal organ. Distribution of exogenous indoleamines: A qualitative study of the rudimentary photoreceptor cells by electron microscopic radioautography

Abstract

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 avried 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.

The avian pineal organ. Distribution of endogenous monoamines; a fluorescence microscopic, microspectrofluorimetric and pharmacological study in the parakeet

“…As a result of this study and other cytophysiologicat inVestigat!ons on the pineal of Lacertilians and biochemical tindings in birds, it is proposed that pathways of synthesis and metabolism of 5-HT are located in SRP cells. The distribution of endogenous arid exogenous (Collin et al, 1976) indoleamines is similar. …”

“…The amines and perhaps also protein(s), are involved in some endocrine mechanisms (for references see Collin et al, 1976). These properties allow to consider the avian pineal organ to be a photo-neuroendocrine organ (Coltin, 1971;Oksche and Hartwig, 1975).…”

Immunocytochemistry and calcium cytochemistry of the mammalian pineal organ: A comparison with retina and submammalian pineal organs

“…In some species, serotonin was localized in pinealocytes autoradiographically and by the Falk Hillarp method (Wartenberg and Baumgarten, 1969;Ueck, 1973;Collin et al, 1976). Using the immunoglobulin-gold method (Vigh, 1987;Vigh and VighTeichmann, 1988) serotonin immunoreaction was found in the neurohormonal terminals of the pinealocytes of the pigeon (Fig.…”

Circadian Information and Messages in the Modified Photoreceptor Cells of the Avian Pineal Organ: Retrospect and Prospect

“…N-acetyl-5-methoxytryptamine (aMT), 5-methoxytryptophol (ML), 5-methoxytryptamine (MT), considered as pineal neurohormones) [9,18,32], From the auto radiographic experiments [6,9,10,18,31], it is concluded that indoles arc produced and stored mainly in the perikaryon and basal pedicle of MP. MP also seem to release indoles directly into the systemic ciculation.…”

“…The principal steps of indole metabolism in birds have been reviewed [ 10,18,33]. The synthesis of indoles undergoes striking circadian and circannual changes [1,30,33].…”