Pineal glands

A hormone synthesized in the pineal gland Certain mental disorders are be lieved to be related to sero tonin levels in the brain )... 

Melatonin. Melatonin (A/-acetyl-5-metlioxytryptaniine) [73-31-4] C 2H gN2O2(250) is secreted from the pineal gland and retina during dark periods of the vertebrate circadian rhythm (65). Melatonin regulates biological rhythms and neuroendocrine function and is formed from serotonin (5-HT). 

Evidence has been put forward that 6-methoxy-l-methyl-l,2,3,4-tetrahydro-j3-carboline may be a component of animal tissues and may be identical with adrenoglomerulotrophine, a factor controlling aldosterone secretion, which is found in the pineal gland where it occurs together with 5-hydroxytryptamine... 

Zipfel, m, tip, point, end, summit lobe, ear, Zirbel-. (Anat.) pineal, -drtise, /. pineal gland, pineal body, -ficlite, -kiefer, /, Swiss pine (Pinua cembra). -nuBB, /. cedar nut (from Pinua cembra). zirka, adv. about, approximately. zifkaBBisch, a. Circassian. 

However, despite its enormous importance to human physiology, no pharmacological compounds targeting the components of the circadian clock system have been identified to date. There are, nevertheless, two therapeutic approaches that are currently used for treatment of circadian-related disorders - full-spectrum and bright light therapy and melatonin therapy. Melatonin is a hormone that is produced by the pineal gland in... 

Neurons within the SCN innervate those hypothalamic areas which have a crucial role in the regulation of the reproductive cycle, mood and sleep/arousal, as well as regions such as the basal forebrain and the thalamus which help to determine the state of arousal. They also project to the pineal gland to govern the synthesis and release of... 

Figure 22.1 Pathways projecting to and from the suprachiasmatic nucleus (SCN). Inputs from photoreceptors in the retina help to reset the circadian clock in response to changes in the light cycle. Other inputs derive from the lateral geniculate complex and the serotonergic, Raphe nuclei and help to reset the SCN in response to non-photic stimuli. Neurons in the SCN project to the hypothalamus, which has a key role in the regulation of the reproductive cycle, mood and the sleep-waking cycle. These neurons also project to the pineal gland which shows rhythmic changes in the rate of synthesis and release of the hormone, melatonin...

Figure 22.3 Possible links in the induction of circadian rhythm between daylight, the suprachiasmatic nucleus and melatonin release from the pineal gland. Some fibres in the optic nerve, projecting from the eye to the lateral geniculate nucleus (LGN) in the thalamus, innervate the suprachiasmatic nucleus (SCN) in the anterior hypothalamus, via the retinohypothalamic tract (RHT). Others project to the SCN from the LGN in the geniculohypothalamic tract (GHT). The release of melatonin into the circulation from the pineal gland (PG) is maximal at night and appears to be controlled partly by noradrenaline released from sympathetic nerves originating in the superior cervical ganglion (SCG). Melatonin receptors are found in the SCN, the removal of which dampens melatonin secretion...

Axelrod, J. 8r Wurtman, R. J. (1966). The formation, metabohsm and some actions of melatonin, a pineal gland substance. Res. Publ. Assoc. Res. Nerv. Merit. Dis. 43, 200-11. 

Axelrod, J. (1974). The pineal gland a neurochemical transducer. Science 184,... 

Cardinali, D. P. (1977). Nuclear receptor estrogen complex in the pineal gland. Modulation by sympathetic nerves. Neuroendocrinology 24, 333-46. 

Haidar, C. Gupta, D. (1990). Sex- and age-dependent nature of the cytoplasmic 5 alpha-dihydrotestosterone (DHT) binding site/receptor in bovine pineal gland. J. Pineal Res. 8, 289-95. 

Karolczak, M., Korf, H. W. Stehle, J. H. (2005). The rhythm and blues of gene expression in the rodent pineal gland. Endocrine 27, 89 100. 

Klein, D. C. (2004). The 2004 Aschoff/Pittendrigh lecture Theory of the origin of the pineal gland - a tale of conflict and resolution./. Biol Rhythms 19, 264-79. 

Moore, R. Y. (1996). Neural control of the pineal gland. Ilehav. Brain Res. 73, 125-30. 

Sanchez, J. J., Abreu, P., Gonzalez-Hernandez, T. et al. (2004). Estrogen modulation of adrenoceptor responsiveness in the female rat pineal gland differential expression of intracellular estrogen receptors. J. Pineal Res. 37, 26-35. 

Vacas, M. I., Lowenstein, P. Cardinali, D. P. (1979). Characterization of a cytosol progesterone receptor in bovine pineal gland. Neuroendocrinology 29, 84-9. 

Serotonin is synthesized from tryptophan in two steps. Tryptophan is hydroxylated by tryptophan hydroxylase, and 5-hydroxytryptophan is decarboxylated to give serotonin. Most serotonin in the body is found in the enterochromaffin cells of the intestinal tract and the pineal gland. Platelets take up and store serotonin but do not synthesize it. 

FIGURE 13-5 The biosynthesis and catabolism of serotonin. Note that in the pineal gland, serotonin is converted enzymatically to melatonin. 

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