Hormonal Melatonin

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...

HT modulates neuroendocrine function 239 5-HT modulates circadian rhythmicity 239 5-HT modulates feeding behavior and food intake 239 Not only does 5-HT have important physiological effects of its own but it is also the precursor of the hormone melatonin 240... 

Gonadal hormones Estrogens Progestins Androgens Neurosteroids Thyroid hormones Melatonin Vasopressin Oxytocin... 

Figure 4.1 Production of the hormone melatonin is low during the day and then increases at night, suggesting that it helps to promote sleep. Many people take melatonin pills to boost levels of the hormone circulating in their blood. 

The pineal gland appears also to play a role in maintaining the mammalian circadian cycle.1081-1083 The concentration of the pineal hormone melatonin (Fig. 27-11) as well as its precursor N-acetylserotonin and the enzyme serotonin N-acetyltransferase (Eq. 30-4) all fluctuate far more than do the concentrations of other metabolites during the 24-h cycle. These metabolites increase over 10-fold concentration at night and decrease by day. During the daytime the serotonin N-acyltransferase, which forms the precursor, is rapidly... 

Some parts of the brain, like the cerebral cortex, are much more highly evolved in humans than in other animals. The pineal gland, however, is a very basic organ that first evolved in primitive species. It is found in lampreys, fish, amphibians, and reptiles, as well as in mammals. The hormone melatonin has also been found in insects and plants. 

The production of melatonin varies over the course of a day. Darkness stimulates the pineal gland to produce melatonin, while the presence of light inhibits the release of this hormone. Melatonin levels are so low during the day lime that they are almost immeasurable. The amount of melatonin starts to increase around 9 p.m. or 10 p.m. 

In patients with DSPS, a delay in the timing of physiological and behavioral systems that demonstrate circadian rhythmicity is reported, compared to normally entrained individuals. This delay is evident in a variety of functions, including secretion of the pineal hormone melatonin (e.g., Ref. 162), thermoregulation, and sleep-wake activity. Individuals with DSPS typically experience difficulty initiat-... 

The hormone melatonin is involved in the control of the circadian system, and has been implicated in the control of sleep [64], Several studies have examined the effectiveness of melatonin as a treatment of insomnia. While some researchers have reported a positive effect [65, 66], others have reported little or no effect [67,68], At present, the magnitude of beneficial effects following melatonin administration to insomniacs is unclear. Furthermore, the mechanism of action of this hormone with relation to sleep initiation, has not yet been fully described [69], Finally, exposure to bright light therapy during the early morning hours has been reported to relieve sleep onset insomnia, even in elderly patients [70], This may be due to the restoration of circadian rhythms in these insomniacs. 

Modern spectroscopic methods and the structure of the hormone melatonin (Opener. Problem 14.26)... 

As mentioned previously, one of the major benefits of nasal drug delivery is the rapid onset of action (tmax)- Migraine treatment takes advantage of this fact. Compared to the orally taken tablet, tmax is much shorter. The neurosecretory hormone melatonin, which is used widely against jetlag, shows a very impressive time profile when administered as a nasal spray. The peak levels of melatonin after nasal administration appear to be 50 times higher than after oral administration. 

Environmental magnetic fields (1.2 pT, 60 Hz) significantly reduce the inhibitory action of physiological levels of the hormone melatonin on the growth of human breast cancer cells in vitro. A similar inhibitory effect is... 

Dubey V, Mishra D, Asthana A, Jain NK (2006) Transdermal delivery of a pineal hormone melatonin via elastic Uposomes. Biomaterials 27(18) 3491-3496... 

Thyrotropin-releasing hormone Growth-hormone-releasing hormone Melatonin... 

The HPG axis is responsible for the cyclic hormone secretion that regulates and controls ovulation and plays a major role in menstruation-related disorders. The menstrual cycle is characterized by cyclic alterations in the production of gonadal hormones (estradiol and progesterone), pituitary hormones (gonadatropins, prolactin, growth hormone), melatonin, and cortisol and in temperature rhythms. Menstruation-related disorders are likely the result of a complex interaction between ovarian steroids and central neurotransmitters, neurohormones, and neuropeptides. The occurrence of physical... 

Wiesenberg, I., Missbach, M., Kahlen, J. P., Schrader, M., and Carlberg, C. (1995) Transcriptional activation of the nuclear receptor RZR alpha by the pineal gland hormone melatonin and identification of CGP 52608 as a synthetic ligand. Nucleic Acids Res. 23, 327-333. 

The pineal gland appears also to play a role in maintaining the mammalian circadian cyde. The concentrahon of fhe pineal hormone melatonin (Fig. 27-11) as well as its precursor N-acetylserotonin and the enzyme serotonin N-acetyltransferase (Eq. 30-... 

In animals, serotonin (5-hydroxytryptamine) is a very important neurotransmitter in the central nervous system and also in the cardiovascular and gastrointestinal systems. The structurally similar hormone melatonin is thought to control the diurnal rhythm of physiological functions. 

The hormone melatonin induces sleep, but serotonin is involved in dreaming both are produced in the pineal gland. If the brain has low serotonin levels, dreaming will not occur. Serotonin is also important in learning, memory, and mood. It is deficient in the brains of depressed patients. Serotonin deficiency can result in an inability to fall asleep at night, panic attacks, loss of concentration, and thoughts of suicide or attempted suicide. 

The indole nucleus is embedded in many biological systems including the essential amino acid tryptophan, the neurotransmitter serotonin, and the mammalian hormone melatonin. Tryptophan is a structural constituent of many proteins as well as the biosynthetic precursor of serotonin, which in turn serves as the precursor of melatonin. Serotonin plays a critical role in neuronal cell formation and maintenance, sleep, cognition, appetite, and mood, while melatonin is a natural bioregulator that induces and maintains sleep [1,2]. 

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