Immunocytochemical localization and circadian variations of serotonin and N-acetylserotonin in photoreceptor cells. Light and electron microscopic study in the teleost pineal organ.

Using two immunocytochemical procedures (i.e., immunofluorescence and the unlabeled peroxidase-antiperoxidase method), the localization of a serotonin(HT)-like and of a N-acetylserotonin (aHT)-like immunoreactivity in the pineal organ of the pike was studied during winter.

In-vitro uptake and metabolism of [3H]-5-hydroxytryptamine in the pineal glands of the rabbit, rat and hamster. A comparative study with the use of autoradiography, chromatography and liquid-scintillation counting.

Pineal glands of rat, rabbit and hamster were incubated during day or night in Merlis' fluid containing [3H]-5-hydroxytryptamine (=[3H]-HT) by the use of a 20-min pulse with or without postincubation in "cold" medium for 15, 30, 45 or 60 min. (1) Selective autoradiographic labeling was observed in sympathetic nerve terminals; this reaction was missing after bilateral surgical removal of the superior cervical ganglia. In contrast, a scarce and diffuse labeling was found in pinealocytes (Pi) and interstitial cells (IC) of both untreated and ganglionectomized animals.

Circadian information and messages in the modified photoreceptor cells of the avian pineal organ: retrospect and prospect.

The modified photoreceptor cell (MP), homologous to the cone-like photoreceptor, is the principal cell type of the avian pineal organ. Two types of secretions (indoles and specific proteins-- pinealins ) are produced in this polarized cell. The synthesis of indoles undergoes striking circadian and circannual changes.

[Retention of indoles in the pineal organ of the bird (Melopsittacus undulatus, Shaw) during its preparation for radioautographic study].

Since high-resolution radioautography (dipping technique) might be very useful for the study of indole metabolism in the pineal cells, the retention of [3H]-indoles has to be examined during the preparation of specimens for electron microscopy (EM). The pineal organ of the parakeet (Melopsittacus undulatus) was used in the present work. 1) Indole metabolism: following uptake of [3H]-5-hydroxytryptophan ([3H]-HW) in vivo and [3H]-5-hydroxytryptamine ([3H]-HT) in vitro in similar seasonal and nycthemeral conditions--all the known pineal indolic metabolites were recovered by thin layer chromatography.

Indole metabolism in the pineal organ of the pigeon with special reference to melatonin-synthesizing cells. In vitro study combining thin layer chromatography, autoradiography and pharmacological treatment.

By means of radioimmunoassay a clear-cut peak of melatonin concentration was found in the pineal organ of the pigeon at the middle of the scotophase (Coisin et al. 1982a). The aim of the present study was to identify the cell type responsible for the nocturnal indole metabolism, including melatonin synthesis, in the pineal of this avian species.