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. MP appear to be receptoneuroendocrine cells which transduce circadian information into 5- methoxyindolic (melatonin, 5-methoxytryptophol, 5-methoxytryptamine) and possibly peptidic neurohormones. Taking into account different stages of differentiation and/or different physiological states (due to cyclic changes) for MP, several mechanisms of transduction of photoperiodic inputs into circadian hormonal outputs have been hypothesized.
D008735:5-Methoxytryptamine / Q000096:biosynthesis; D000818:Animals; D001717:Birds; D002940:Circadian Rhythm; D007211:Indoles / Q000096:biosynthesis; D008550:Melatonin / Q000096:biosynthesis; D010452:Peptide Biosynthesis; D010455:Peptides; D010786:Photoreceptor Cells / Q000378:metabolism*; D010870:Pineal Gland / Q000378:metabolism*
D007211:Indoles; D010455:Peptides; C016320:polypeptide pineal extract; D008735:5-Methoxytryptamine; C002465:methoxytryptophol; D008550:Melatonin