The Pineal Organ, Its Hormone Melatonin, And The Photoneuroendocrine System (advances In Anatomy, Embryology And Cell Biology) (volume 146)

The vertebrate pineal organ rhythmically synthesizes and secretes melatonin during nighttime and forms an essential component of the photoneuroendocrine system which allows humans and animals to measure and keep the time. Regulation of the melatonin biosynthesis depends on signals from photoreceptors perceiving and transmitting environmental light stimuli and endogenous oscillators generating a circadian rhythm which is independent from any environmental time cue (zeitgeber). In nonmammalian species the photoreceptors responsible for regulating melatonin biosynthesis reside within the pineal organ itself. In several nonmammalian species (e.g., lamprey, zebra fish, house sparrow, chicken) the pineal organ is also capable of generating circadian rhythms and thus serves all key functions of the photoneuroendocrine system: photoreception, endogenous rhythm generation, and production of neurohormones. These may even be accomplished by a single "photoneuroendocrine" cell. In mammals the pineal organ has lost both the direct light sensitivity and the capacity of generating circadian rhythms, and melatonin biosynthesis is regulated by retinal photoreceptors and a circadian oscillator located in the suprachiasmatic nucleus of the hypothalamus. Due to this spatial separation the photoneuroendocrine system of mammals comprises neuronal and neuroendocrine pathways which interconnect its components. The neuronal pathways involve circuits of both the central and the peripheral nervous systems, and as an important final link noradrenergic sympathetic nerve fibers. The suprachiasmatic nucleus appears as a major target of melatonin in mammals. The pineal hormone may thus be involved in a feedback loop of the mammalian photoneuroendocrine system. The present comparative contribution considers, after a short survey of classical findings on the phylogenetic development and the gross anatomy of the pineal complex, cytoevolutionary and cell biological aspects of the various types of pinealocytes as well as the afferent and efferent innervation of the pineal organ (pinealofugal and pinealopetal neuronal pathways). Moreover, emphasis is placed on receptor mechanisms, second messenger systems (Ca2+ and cyclic AMP), transcription factors (e.g, CREB and ICER), and their roles for regulation of melatonin biosynthesis. Finally, the action, targets, and receptors of melatonin are dealt with. The synoptic approach of this contribution, which combines anatomical and ultrastructural findings with cell and molecular biological results, confirms the functional significance of the melatonin-synthesizing pineal organ as an important component of the photoneuroendocrine system and stresses the importance of this organ as a model to study signal transduction mechanisms both in photoreceptors and in neuroendocrine cells.

Provides comprehensive, updated information on the structure, and cell and molecular biology of the vertebrate pineal organ, which is the source of the "timing hormone" melatonin.

John A. McNulty

The pineal gland and its hormone, melatonin, have received considerable attention recently for their sedative and other actions. In that regard, this book is timely and provides a concise review of the comparative morphology and function of this photoneuroendocrine organ. The authors succeed admirably in leading the reader from the morpho-functional evolutionary changes in the pineal gland through chapters on the innervation and receptor-mediated transduction of melatonin synthesis to a discussion of pineal transcription factors, ending with a chapter on the actions, targets, and receptors of melatonin. This book is part of the series Advances in Anatomy, Embryology, and Cell Biology, which publishes critical articles covering special fields. Accordingly, any student of the pineal gland will find parts or all of this review useful to their studies. This review strikes a nice balance between the classic literature and the most recent research developments through 1997. Those subjects that are covered most extensively deal with the innervation of the gland, receptors, and mechanisms of transduction. A number of previously unpublished photographs are also included. The overall high quality of this book is consistent with the seminal contributions of the authors to the field. I highly recommend it to any pinealogist interested in a helpful compilation of the research advances in the selected topics.

This book offers a synoptic view of comparative anatomical, ultrastructural, cell and molecular biological investigations of the pineal organ. It considers morphological, immunocytochemical and functional features of pineal photoreceptors and neuroendocrine pinealocytes as well as the afferent and efferent innervation of the pineal organ. Special emphasis is placed on receptor mechanisms, second messenger systems (Ca2+ and cyclic AMP), transcription factors (e.g. cyclic AMP response element binding protein, CREB, and inducible cyclic AMP early repressor, ICER) and their roles for regulation of melatonin biosynthesis. Finally, the action, targets and receptors of melatonin are dealt with. The data presented stress the functional significance of the pineal organ and its hormoe melatonin as important components of the photoneuroendocrine system which allows man and animals to measure and keep the time. They also prove the pineal organ as a very suitable model to study signal transduction mechanisms in both photoreceptors and neuroendocrine cells by means of a variety of modern techniques. Front Matter....Pages I-IX Introduction....Pages 1-8 Phylogenetic Development and Gross Anatomy of the Pineal Complex....Pages 9-11 Pineal Cell Biology and Innervation....Pages 13-44 Receptor Mechanisms and Second Messenger Systems Involved in the Regulation of the Melatonin Biosynthesis....Pages 45-58 Pineal Transcription Factors and Their Possible Roles for the Regulation of the Melatonin Biosynthesis....Pages 59-71 Action, Targets, and Receptors of Melatonin....Pages 73-77 Summary....Pages 79-79 Back Matter....Pages 81-101 This book presents an updated view on structure, cell and molecular biology of the vertebrate pineal organ, which is the source of the "timing hormone" melatonin