Biological Sciences
Pineal Gland
The pineal gland is a small, pinecone-shaped gland in the brain that produces the hormone melatonin, which helps regulate sleep-wake cycles and circadian rhythms. It is also involved in the body's response to light and darkness. The pineal gland is considered a part of the endocrine system and is often referred to as the "third eye" due to its association with light sensitivity.
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12 Key excerpts on "Pineal Gland"
- Davis Langdon, Paul J. Rosch(Authors)
- 2014(Publication Date)
- Routledge(Publisher)
497 FUNDAMENTAL RESEARCH: INTRODUCTION The Pineal Gland is arguably both the most misunderstood and underrated endocrine gland in the human body. Until 40 years ago, almost nothing was known about the pineal; it was considered unimportant and physiologically useless. Yet, René Descartes stated that the pineal is the “seat of the soul,” and Eastern religions have described the pineal as the mysterious “third eye,” the seat of wisdom, or the source of inner light. Although these beliefs were based on some rudi-mentary knowledge of the pineal as being photosensitive, the alignment of the pineal with spirituality has, more likely than not, been a deterrent to serious scientific research, relegating the pineal to the realm of the unknowable (see Zrenner 1 for a history of the Pineal Gland). Complicating matters further, Descartes’s expression linking the pineal and the soul generally is misunderstood. The philosopher, who is undoubtedly even better known for his exclamation, “cogito ergo sum” (I think, therefore I am/ exist), believed that the ability to think is irrefutable evidence that the mind exists. His dualistic philosophical system divides the universe into mutually exclusive but interacting elements of spirit/mind or God and matter. Descartes’s “seat of the soul” expression stems from his belief that the pineal is the interface between the spiritual and the material worlds. It is my contention that the pineal is the master gland and the major energy transducer (and physiological regulator) between the energy surrounding us and our internal physiology. OVERVIEW OF THE Pineal Gland Only in the last 30 to 40 years has an accurate understanding of the functions of the pineal begun to emerge. Most of this understanding has stemmed from the isolation of melatonin ( N -acetyl-5-methoxytryptamine), the major pineal hormone. 2 The pineal has the ability to transform neural input into endo-crine output.
eBook - ePub- Paul V. Malven(Author)
- 2019(Publication Date)
- CRC Press(Publisher)
Chapter 10Pineal Gland
The Pineal Gland is a small diverticulum of ependymal cells dorsal to the third ventricle and adjacent to the epithalamus. The name derives from the Latin term pinea (pine cone), the shape of which it resembles. Because the Pineal Gland is not bilaterally represented as are most CNS structures, ancient scholars attributed important functions to it. The terms pineal gland and pineal organ are both used, and each name is correct. Pineal Gland, the name used in this book, is an appropriate term because the cells secrete a hormone (melatonin) into the blood. Pineal organ is also an appropriate name because the structure is one of several circumventricular organs (see Chapter 4 ). The cells of the Pineal Gland are called pinealocytes, and they function as neuroendocrine transducers as described in Chapter 1 (Figure 1-1 ). This transduction consists of converting action potentials (AP) of postganglionic sympathetic neurons into melatonin secretion by the pinealocytes.Changes in the Pineal Gland during evolution leading up to mammals reflect a progressive loss of photoreception by the pineal structure. In amphibians and lower species, the Pineal Gland appears to function as a third eye, having photoreception and electrical activities consistent with visual function. Although visual functions were lost during evolutionary development, the Pineal Gland of birds and mammals retains the capacity to be influenced by ambient light. The Pineal Gland of birds appears, at least in part, to be directly sensitive to ambient light passing through the cranium. In mammals, the pinealocytes are modulated by ambient light, but this effect is mediated by retinal photoreception occurring in the eye.The gross morphology of the Pineal Gland ranges from a spherical shape in ruminant ungulates to a cylindrical structure containing deep and superficial portions in rodent species (Rollag et al., 1985). The pineal tissue consists of non-neuronal parenchymal cells, the pinealocytes, that share some antigenic characteristics with retinal cells but not neuroglia (Korf et al., 1986). The Pineal Gland contains a few neuroglial cells but lacks neuronal perikarya. Although there is a tissue connection between the Pineal Gland and adjacent epithalamus, there do not appear to be any axons passing through this connecting neural tissue. However, there are numerous axonal terminals in the Pineal Gland; they are derived from postganglionic axons that originate outside the CNS in the superior cervical ganglion (SCG). The SCG is the rostral-most ganglion of the sympathetic chain, and it contains the perikarya of postganglionic sympathetic neurons. The perikarya in the SCG are activated by preganglionic axons originating in the CNS. Postganglionic axons enter the Pineal Gland from outside the CNS and innervate pinealocytes. Norepinephrine (NE) is the neurotransmitter released at these secretomotor terminals (see Figure 1-1
eBook - ePub- Anthony W. Norman, Helen L. Henry(Authors)
- 2014(Publication Date)
- Academic Press(Publisher)
Chapter 16The Pineal Gland
The Pineal Gland was identified as a distinct structural component of the vertebrate brain for several centuries prior to its description in the human by Galen of Pergamon (c. 130–200). It is now understood that the main function of the pineal is to receive information about the current state of the light–dark cycle from the environment and convey this information through the secretion of the hormone melatonin to the internal physiological systems of the body. Relative to other endocrine and neuroendocrine systems, the Pineal Gland has undergone a great deal of change during its evolutionary development. In cold-blooded vertebrates, the cells of the Pineal Gland include photoreceptors that contact neurons to communicate with other organs in the body. The avian Pineal Gland is also a directly photosensory organ and secretes melatonin in response to this signal. In mammals, pinealocytes producing melatonin have replaced photoreceptors and the gland receives its information about light and darkness from the retina through multiple neuronal connections. Melatonin is secreted during the dark period of the day and, through its elevated blood levels, informs, through specific cell receptors, the peripheral organs and tissues regarding the light/dark cycle. In addition to its function of sending information to the periphery regarding light and dark, melatonin from the Pineal Gland also contributes to the entrainment of the central SCN oscillator to the light–dark cycle. This chapter covers the anatomical features of the Pineal Gland, the synthesis and secretion of melatonin, the biological actions of melatonin, and various clinical aspects related to the Pineal Gland.
- George H. Gass, Harold M. Kaplan(Authors)
- 2020(Publication Date)
- CRC Press(Publisher)
Chapter 3THE Pineal Gland AND MELATONIN
Jerry Vriend and Nancy A.M. Alexiuk
CONTENTS Introduction Anatomy Phylogenetic Considerations The Mammalian Pineal Gland Anatomy Ultrastructure of Mammalian Pinealocytes Blood Supply Innervation Biochemistry Purification and Identification of Melatonin Peptides in the Pineal Gland Sythesis and Regulation of Melatonin Secretion Distribution and Metabolism of Melatonin Assays for Melatonin Physiological Effects of the Pineal and Melatonin in Control of Endocrine Systems Effects on the Hormones of Reproduction in Males Effects on the Hormones of Reproduction in Females The Pineal and Thyroid Hormones Pineal-Thyroid and Pineal-Gonadal Axes: Are They Independent? Effects on the Adrenal Gland Effects on Growth Hormone Secretion Other Effects of the Pineal Gland The Pineal Gland and the Central Nervous System Melatonin Binding Sites Melatonin and Second Messenger Systems Melatonin and Neurotransmitters Pineal Research and Circadian Rhythms Melatonin: Psychopharmacological Effects and Clinical Implications Pineal Gland and Seizures Pineal and Melatonin: Oncology and Immunology Melatonin and Immune Response Pineal Tumors ReferencesINTRODUCTION
The inclusion of a chapter on the Pineal Gland suggests that the Pineal Gland has a kinship with the other classical endocrine glands. Like other glands that deposit hormones into the blood vascular system, the Pineal Gland is a highly vascular structure. It is now well documented that the Pineal Gland secretes at least one active substance, N-acetyl-5-methoxy-tryptamine, commonly known as melatonin. This indole has been detected both in the Pineal Gland, from which it was originally isolated,1 , 2 and in the circulation of amphibians,3 birds,4 fish,5 , 6 and a large number of mammalian species including man.7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16
eBook - PDFMelatonin
Therapeutic Value and Neuroprotection
- Venkatramanujan Srinivasan, Gabriella Gobbi, Samuel D. Shillcutt, Sibel Suzen, Venkatramanujan Srinivasan, Gabriella Gobbi, Samuel D. Shillcutt, Sibel Suzen(Authors)
- 2014(Publication Date)
- CRC Press(Publisher)
19 3 Pineal Gland Volume and Melatonin Niyazi Acer, Süleyman Karademir, and Mehmet Turgut 3.1 INTRODUCTION Circumventricular organs are located in or near the wall of the third ventricle, the cerebral aque-duct of Sylvius, and the fourth ventricle, may be of functional importance with regard to the cerebrospinal fluid (CSF) composition, hormone secretion into the ventricles (Duvernoy and Risold 2007, Horsburgh and Massoud 2013, McKinley et al. 1990). The Pineal Gland is one of the circum-ventricular organs in humans, having no blood–brain barrier (BBR) and being attached to the roof of the posterior aspect of the third ventricle. It is located beneath the splenium of the corpus cal-losum (Figure 3.1). There is no direct connection between the central nervous system (CNS) and the Pineal Gland. The Pineal Gland likely affects CNS functions as a result of the release of these hormones into the general circulation and into the brain through BBR (Acer et al. 2011). Aaron Lerner identified melatonin (Mel) 50 years ago, and it was measured in peripheral body fluids 30 years ago (Arendt 2006). It has been 25 years since bright white light was shown to sup-press Mel totally and around 20 years since Mel-binding sites in the suprachiasmatic nuclei (SCN) and pars tuberalis were discovered (Arendt 2006). All of them have enhanced our knowledge con-cerning the role and effects of Mel in humans (Arendt 2006). The Pineal Gland produces Mel, which helps regulate day–night cycles known as the body’s cir-cadian rhythm (Acer et al. 2011). Mel secretion rises in the dark and occurs at a low level in daylight (Arendt 2006, Standring 2008). Thus, its secretion fluctuates seasonally with changes in day length. Mel may suppress gonadotropin secretion; removal of the pineal from animals causes premature sexual maturation (Arendt 2006, Standring 2008). The Pineal Gland is an endocrine gland of major regulatory importance.
eBook - PDF- Gerald Litwack(Author)
- 2012(Publication Date)
- Academic Press(Publisher)
CHAPTER 5 The ß-Adrenergic Receptor and the Regulation of Circadian Rhythms in the Pineal Gland Julius Axelrod and Martin Zatz 1. Biosynthesis of Melatonin 250 Effects of Environmental Lighting on Melatonin Synthesis .. 251 II. Circadian Rhythms in the Pineal Gland 252 A. Metabolism of Indoleamines in Pineal Organ Culture 254 B. How Circadian Rhythms in the Pineal Are Generated 256 C. Regulation of Pineal Responses to ß-Adrenergic Stim-ulation 257 111. Conclusion 266 References 266 Experiments during the last decade have shown that the Pineal Gland is a useful organ for studying the relationship between neuro-transmitters and responsive cells as well as circadian rhythms. The pineal is located between the cerebral hemispheres and is innervated by noradrenaline-containing nerves whose cell bodies lie in the superior cervical ganglia in the neck (Kappers, 1960). It contains high levels of biogenic amines such as serotonin, noradrenaline, histamine 249 250 Axelrod and Zatz (Giarman and Day, 1959), and melatonin (5-methoxy-N-acetyltryp-tamine) (Lerner et al., 1958). Melatonin has been shown to have many potent physiological ef-fects. It exerts inhibitory effects on the gonads in mammals ( Wurtman et al., 1968). It lowers the luteinizing hormone (LH) level in plasma and prevents the elevation of LH in the pituitary (Fraschini et al., 1971). The administration of melatonin results in a variety of de-creased pituitary-gonadal functions and also affects the activities of several endocrine organs (Reiter, 1973). Melatonin is the most potent agent for causing contractions of melanophores in frog and fish skin (Lerner et al., 1958). It is possible that the Pineal Gland, through methoxyindole secretion, serves as a time-measuring device in birds (Gaston and Menaker, 1968). I. BIOSYNTHESIS OF MELATONIN Soon after the isolation and identification of melatonin, the enzyme that synthesizes this methoxyindole in the pineal was characterized (Axelrod and Weissbach, 1961).
eBook - ePubHormonal Signaling in Biology and Medicine
Comprehensive Modern Endocrinology
- Gerald Litwack(Author)
- 2019(Publication Date)
- Academic Press(Publisher)
Chapter 6The Pineal as a Gland and Melatonin as a Hormone
Richard J. Wurtman Massachusetts Institute of Technology, Cambridge, MA, United StatesAbstract
The human pineal is an unpaired midline organ, derived from and surrounded by brain tissue, which secretes a hormone, melatonin, into the blood and the cerebrospinal fluid, principally during the daily dark period. The melatonin then activates receptors on brain neurons to provide a time-signal for various circadian rhythms, to promote sleep onset, and principally, sleep maintenance during the night. The deficiency in nocturnal plasma melatonin levels that often occurs among older people, caused by the unexplained tendency of their pineals to develop progressive calcification, is a frequent cause of decreased sleep efficiency, manifest as the tendency to awaken for prolonged periods during the night. This can be treated by “hormone replacement therapy” using small doses of oral melatonin, just sufficient to raise its blood levels to what they were nocturnally earlier in life.Melatonin's synthesis starts with the 5-hydroxylation of the essential amino acid tryptophan, followed by its decarboxylation to form serotonin (5-hydroxytryptamine). In the pineal, but to a very limited extent elsewhere in the body, this serotonin is converted to melatonin by enzymes that acetylate its amine nitrogen, forming N-acetylserotonin, which is then O-methylated to form the melatonin (5-methoxy-N-acetyltryptamine). When humans and other mammals are in darkness the electrical activity of, and norepinephrine release from, the pineal's sympathetic nerves are maximal, and the intrasynaptic norepinephrine acts on pineal beta receptors, forming cyclic-AMP and activating the enzymes that will convert the serotonin to melatonin. Conversely, exposure to environmental lighting diminishes the pineal's sympathetic activity and its synthesis of melatonin. In submammalian vertebrates the pineal organ often contains photoreceptors, through which light exposure can directly affect brain.
eBook - PDFHistologic Basis of Mouse Endocrine System Development
A Comparative Analysis
- Matthew Kaufman, Alexander Yu. Nikitin, John P. Sundberg(Authors)
- 2016(Publication Date)
- CRC Press(Publisher)
The information that passes along this route therefore influences many physiological, endocrine, and psychomotor functions concerning the sleep–wake cycle. Melatonin released from the pineal therefore plays a critical role in regulating such cycles. Noradrenergic sympathetic nerve terminals innervate the gland and regulate melatonin production and release. In an early study, when there was in fact some doubt expressed as to whether the Pineal Gland was an endocrine organ, it was its secretion of melatonin and the influence of this substance on various endocrine organs that convinced the authors of its endocrine status. 10 This substance had 136 Histologic Basis of Mouse Endocrine System Development previously been shown to have an effect on the rat and hamster ovary 11,12 and hamster testis 13 and on the secretion of luteinizing hormone (LH) from the pituitary gland. 14 It was also known at that time that the Pineal Gland had an influence on the timing of onset of puberty in man and in animals, while pinealectomy could advance the onset of puberty in animals. 15 This study confirmed that melatonin had a positive influence on testicular development. 10 EMBRYOLOGICAL FEATURES IN MAMMALS In all mammalian species studied, the Pineal Gland arises in the dorsal midline from the caudal part of the roof plate of the third ventricle of the brain. It develops from an evagination of the most caudal part of the prosencephalon, just rostral to the cranial limit of the mesencephalic flexure. At this relatively early stage of development, therefore, the forebrain contains a central cavity termed the third ventricle, and this corresponds to the lumen of the prosencephalon. Very shortly afterward, the prosencephalic vesicle develops a number of evaginations. The earliest of these to appear are the paired optic stalks and, ventrally in the midline, the pituitary stalk or hypophysis cerebri .
eBook - PDF- Peter K.T. Pang(Author)
- 1991(Publication Date)
- Academic Press(Publisher)
Armed T vith this information, reproductive scientists thereafter were able to design appro-priate experiments to examine the relationship between the Pineal Gland and reproduction. 269 VERTEBRATE ENDOCRINOLOGY: Copyright © 1991 by Academic Press, Inc. FUNDAMENTALS AND BIOMEDICAL IMPLICATIONS All rights of reproduction in any form reserved. Volume 4, Part 270 Russel J.Reiter Those species that have had the greatest utility in clarifying how pineal secretory products modulate sexual physiology are commonly referred to as being photoperiodic. In these species, the prevailing light:dark environment exercises a major control over the functional status of the reproductive system, with the Pineal Gland serving as the intermediary between the photo-period and the reproductive system (Reiter, 1983). In reality, all mammals may be photoperiodic, with the differences among species being in the degree of their photoperiodism (i.e., the magnitude of the responses to photoperiodic manipulations). Examples of some highly photoperiodic species whose ex-perimental use has provided a significant portion of the information now available relating to pineal-reproduction interactions include the Syrian ham-ster (Mesocricetus auratus) (Reiter, 1985a), the Djungarian hamster (Phodo-pus sungoms) (Hoffmann, 1978a), the white-footed mouse (Peromyscus leu-copus) (Petterborg, 1986), and certain breeds of domestic sheep (Kennaway, 1984). The current review will primarily consider and compare the reproduc-tive responses of these species to photoperiodic perturbations and pineal manipulations, although information garnered from studies using other mam-mals will be included as well. II. NEURAL CONNECTIONS OF THE Pineal Gland As an end organ of the visual system (Fig. 1), the Pineal Gland is markedly influenced by photic information impinging on the retinas of mammals.
- Toshiaki J. Hara, Barbara Zielinski(Authors)
- 2006(Publication Date)
- Academic Press(Publisher)
Finally, indication was provided that the pineal organ and melatonin modulated neuroendocrine functions including growth and reproduction. However, these early studies were based on in vivo experiments, and they often led to conflicting results. The available data di V ered with gender, photoperiod, temperature, and reproductive stage. Molecular and pharmaco-logical studies provided the first evidence that the pituitary is a target for melatonin, which modulates the release of pituitary hormones (Falco ´n et al. , 2003a). The e V ects are complex because they depend on the concentration and the season. In brief, it is today well admitted that the pineal organ is a key component in the circadian organization of fish, and that it mediates the synchronizing e V ects of photoperiod on crucial physiological functions and behaviors. Melatonin appears as one neurohormonal messenger mediating these e V ects. However, a clear ‐ cut picture of its modes of action is still missing. This awaits a more precise identification of its molecular and cellular targets, and elucidation of its mode of action. It is also of crucial importance to understand how are produced melatonin and other output signals from the pineal, in response to the daily changes in illumination. Our knowledge on this matter is reviewed below. 2 Pinealectomy can cause either marked changes in the free running period, or splitting of the activity rhythm or arrhythmicity. 6. MOLECULAR AND CELLULAR REGULATION OF PINEAL ORGAN 245 2. FUNCTIONAL ORGANIZATION OF THE PINEAL 2.1. Anatomy The anatomical organization of the fish pineal organ has been described in many fish species (Ekstro ¨m and Meissl, 1997; Falco ´n, 1999). The pineal organ is generally organized in two parts, an end vesicle connected to the dorsal epithalamus by a stalk (Figure 6.1).
eBook - PDF- G. E. W. Wolstenholme, Julie Knight, G. E. W. Wolstenholme, Julie Knight(Authors)
- 2009(Publication Date)
- Wiley(Publisher)
exp. Nturol. 20, 563-570. 34 DISCUSSION KLEIN, D. C., BERG, G. R. and WELLER, J. (1970) Science 168,979980. KLEIN, D. C., BERG, G. R., WELLER, J. and GLINSMANN, W. (1970) Science 167, 1738-1740. MACHADO, A. B. M. and LEMOS, V. P. J. (1970) J. Neuro-oisc. Rel. 32, in press. MILINE, R., DEVEEERSKI, V. aFd KRSTIC, R. (1969) Acta. auat. 73, suppl. 56, 293-300. MILINE, R., DEVEEERSKI, V,., SIKAEKI, N. and KRSTIC, R. (1970) Hormones, in press. MILINE, R., WERNER, R., SCEPOVIC, M., DEVEEERSKI, V. and MILINE, J. (1969) Bull. Ass. TRUEMAN, T. and HERBERT, J. (1970) Z. ZellforJch. nzikrosk. Anat. 1% 83-100. VOGT, M. (1969) Br. J. Pharmac. 37, 325-337. WHITBY, L. G., AXELROD, J. and WEIL-MALHERBE, H. (1961)J. Pharmac. exp. Ther. 132, WURTMAN, R. J., AXELROD, J. and KELLY, D. E. (1968) The Pineal. New York and London: WURTMAN, R. J. and KAMMER, H. (1966) New Eq1.J. Med. 274,1233-1237. Anat. 145,289-293. 193-201. Academic Press. NEURAL CONTROL OF INDOLEAMINE METABOLISM IN THE PINEAL JULIUS AXELROD Laboratory nf Clinical Science, National Institute nf Mental Health, Betkesda, Maryland DURING the past decadc considerable new information about the bio- chemistry of the Pineal Gland has been obtained. The initial stimulus was the isolation and identification of melatonin (N-acetylmethoxytryptaniine) in the bovine Pineal Gland (Lerner, Casc and Heinzelman 1959). This discovery led to the identification of other indoles in the pineal, such as serotonin, 5-hydroxyindole acetic acid, 5-methoxyindole acetic acid, 5-hydroxytryptophol and 5-methoxytry-ptophol (Giarman and Day 1959; McIsaac et al. 1965). In addition, other biogenic amines, noradrenaline, dopamine and histamine, were also found to be highly localized in the mammalian pineal (Pellegrino de Iraldi and Zieher 1966; Machado, Faleiro and DaSilva 1965). BIOSYNTHESIS OF MELATONIN The presence of melatonin in the pineal led to a search for the enzyme that makes this compound and the individual steps in its biosynthesis.
eBook - PDF- David Evered, Sarah Clark, David Evered, Sarah Clark(Authors)
- 2009(Publication Date)
- Wiley(Publisher)
Endocrinology 116:2167-2173 Watts AG, Swanson LW 1984Evidence for a massive projection from the suprachiasmatic nucleus to a subparaventricular zone in the rat. Neurosci Abstr 10:611 Wheler GHT, Weller JL, Klein DC 1979 Taurine: stimulation of pineal N-acetyltransferase activity and melatonin production via a beta-adrenergic mechanism. Brain Res 166:65-74 gy 29:350-361 Melatonin and the brain in photoperiodic mammals M. H. HASTINGS, J. HERBERT, N. D. MARTENSZ and A. C. ROBERTS University of Cambridge, Department of Anatomy, Downing Street, Cambridge CB2 3DY, UK Abstract. The reproductive cycle of photoperiodic species is driven by seasonal changes in daylength. The Pineal Gland transduces photic information into an endocrine signal. The duration of the nocturnal bout of melatonin secretion is a direct indicator of night- length. The circadian rhythm of melatonin production is driven by a multisynaptic pathway from the suprachiasmatic nuclei (SCN), via the parvocellular portion of the paraventricular nucleus to the preganglionic sympathetic neurons of the thoracic spinal cord. The melatonin signal acts as an interval timer. The cellular basis of the detection of the signal is unknown. The site of detection is possibly within the anterior hypothalamus. The SCN are not essential components of the system that responds to the pineal interval timer. Photoperiod and the pineal melatonin signal have pronounced effects on the function of endogenous opioids, which are probably related to changes in the neuroendocrine mechanisms that regulate gonadotropin release. 1985 Photoperiodism, melatonin and the pineal. Pitman, London (Ciba Foundation Sym- posium 117) p 57-77 Seasonal changes in daylength are used in two major ways to ensure that the offspring of photoperiodic mammals are conceived (and hence born) in the most opportune season. Firstly, they stimulate reproductive activity at the optimum time and, secondly, they suppress reproduction in unfavourable seasons.
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