Endocrine - Pineal Development
Introduction
The pineal gland (epiphysis cerebri) has an important role in the sleep/wake daily cycle and reproductive development. The gland is thought to evolutionarily to have been positioned as to be exposed to light, and hence remains a regulator of cyclic rhythms associated with day/night and day length. The pineal hormone (melatonin) has targets both in the nervous system and in many different peripheral tissues.
In humans, the postnatal melatonin levels in premature infants is lower and delayed, but not different when calculated from conception date. Other factors such as preeclampsia, growth restriction, and nursery lighting can cause altered rhythm development. The same study has also shown that full-term infants born at home and full-term twins born in the hospital had significantly lower metabolite excretion levels than hospital-born singleton infants at the same ages despite similar body weights. (More? Kennaway DJ, etal, 1996)
In other species, it has been shown that maternal melatonin crosses the placenta into fetal circulation and may provide photoperiodic information during fetal development that influences later postnatal circadian (daily day/night) and seasonal (day length) rhythms.
- part of epithalmus - neurons, glia and pinealocytes
- pinealocytes secrete melatonin - cyclic nature of activity, melatonin lowest during daylight
- inhibit hypothalamic secretion of GnRH until puberty, pineal gland then rapidly regresses.
- other activities - possibly gamete maturation, antioxidant effect, protect neurons?
Endocrine System Development | Lecture - Endocrine Development | Lecture - Head Development | original page
Development Overview
- Neuroectoderm - prosenecephalon then diencephalon
- caudal roof, median diverticulum, epiphysis
- Initially a hollow diverticulum, cell proliferation to solid, pinealocytes (neuroglia), cone-shaped gland innervated by epithalamus
- epithalamus consists of the pineal gland and habenular nuclei
Melatonin
Melatonin is synthesized from the amino acid tryptophan within the pinealocytes.
Melatonin release is stimulated by darkness and inhibited by light and is said to have neurological "chronobiotic" properties for resynchronization of sleep and circadian rhythms disturbances. In the periphery, melatonin is also involved in the regulation of several complex cycles: seasonal reproduction, body weight and energy balance.
The hormone melatonin acts through receptors (high affinity G protein-coupled) embedded in the cell membrane. Three different receptor subtypes have been identified in mammals: MT1 (Mel 1a) and MT2 (Mel 1b) and a putative binding site called MT3.
Melatonin levels can be monitored by urinary excretion of the melatonin metabolite 6-sulfatoxymelatonin (aMT.6S).
Abnormalities
- Pineal Hypoplasia associated with retinal disease.
- Pineal Tumours in children are associated with abnormal puberty development.
Molecular Development
DARPP-32 (Dopamine- and cAMP-regulated phosphoprotein of 32 kDa) is involved in the retinal pathway transmitting photic information that resets the circadian clock.
References
Online Textbooks
- Pineal Gland and Cancer-An Epigenetic Approach to the Control of Malignancy: Evaluation of the Role of Melatonin Eurekah Bioscience Collection -> Neuropharmacology
- Endocrine changes in puberty Endocrinology -> The gonad
- Second Malignancies Cancer Medicine -> Section 24: The Eye -> 85. Neoplasms of the Eye -> Pediatric Ophthalmic Oncology: Ocular Diseases
- The Action of Melatonin on Experimental in-Vivo Tumors Eurekah Bioscience Collection -> Neuropharmacology -> Pineal Gland and Cancer-An Epigenetic Approach to the Control of Malignancy: Evaluation of the Role of Melatonin -> Effect of Melatonin on Tumor Growth
- Potential Significance of (Patho)Physiological Changes of Melatonin for the Aetiology of Cancer Eurekah Bioscience Collection -> Neuropharmacology -> Pineal Gland and Cancer-An Epigenetic Approach to the Control of Malignancy: Evaluation of the Role of Melatonin
- Effects of Exogenous Melatonin AHRQ Evidence reports and summaries -> AHRQ Evidence Reports, Numbers 61 - 119 -> 108. Mel
Reviews
- Weinert D. [See Related Articles] Ontogenetic development of the mammalian circadian system. Chronobiol Int. 2005;22(2):179-205.
- Macchi MM, Bruce JN. [See Related Articles] Human pineal physiology and functional significance of melatonin. Front Neuroendocrinol. 2004 Sep-Dec;25(3-4):177-95.
- Barrenetxe J, Delagrange P, Martinez JA. [See Related Articles] Physiological and metabolic functions of melatonin. J Physiol Biochem. 2004 Mar;60(1):61-72.
- Ekstrom P, Meissl H. [See Related Articles] Evolution of photosensory pineal organs in new light: the fate of neuroendocrine photoreceptors. Philos Trans R Soc Lond B Biol Sci. 2003 Oct 29;358(1438):1679-700.
- Thomas L, Drew JE, Abramovich DR, Williams LM. [See Related Articles] The role of melatonin in the human fetus (review). Int J Mol Med. 1998 Mar;1(3):539-43.
Articles
- Saito S, Tachibana T, Choi YH, Denbow DM, Furuse M. [See Related Articles] ICV melatonin reduces acute stress responses in neonatal chicks. Behav Brain Res. 2005 Dec 7;165(2):197-203.
- Kennaway DJ, Goble FC, Stamp GE. [See Related Articles] Factors influencing the development of melatonin rhythmicity in humans. J Clin Endocrinol Metab. 1996 Apr;81(4):1525-32.
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- Endocrine Development - All (14277) Review (4620) Free Full Text (3140)
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External Links
- NIH Child Health and Human Development (USA) Pineal Gland and Chronobiology: Regulation of Pineal Function
- University of Cincinnati SURVEY OF ENDOCRINE ORGANS
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Cite this page: Hill, M.A. (2024, June 17) Embryology Endocrine - Pineal Development. Retrieved from https://embryology.med.unsw.edu.au/embryology/index.php/Endocrine_-_Pineal_Development
- © Dr Mark Hill 2024, UNSW Embryology ISBN: 978 0 7334 2609 4 - UNSW CRICOS Provider Code No. 00098G