ISSN 1308-8734 | E-ISSN 1308-8742
Review
A Review of Melatonin, Its Receptors and Drugs
1 Department of Emergency Medicine, Department of Medical Pharmacology, Atatürk University School of Medicine, Erzurum, Turkey  
2 Department of Psychiatry, Department of Medical Pharmacology, Atatürk University School of Medicine, Erzurum, Turkey  
3 Department of Neurology, Atatürk University School of Medicine, Erzurum, Turkey  
4 Department of Medical Pharmacology, Atatürk University School of Medicine, Erzurum, Turkey.  
Eurasian J Med 2016; 48: 135-141
DOI: 10.5152/eurasianjmed.2015.0267
Key Words: Melatonin, receptors, agonists, pineal gland
Abstract

After a Turkish scientist took Nobel Prize due to his contributions to understand clock genes, melatonin, closely related to these genes, may begin to shine. Melatonin, a hormone secreted from the pineal gland at night, plays roles in regulating sleep-wake cycle, pubertal development and seasonal adaptation. Melatonin has antinociceptive, antidepressant, anxiolytic, antineophobic, locomotor activity-regulating, neuroprotective, anti-inflammatory, pain-modulating, blood pressure-reducing, retinal, vascular, anti-tumor and antioxidant effects. It is related with memory, ovarian physiology, and osteoblast differentiation. Pathologies associated with an increase or decrease in melatonin levels are summarized in the review. Melatonin affects by four mechanisms: 1) Binding to melatonin receptors in plasma membrane, 2) Binding to intracellular proteins such as calmoduline, 3) Binding to Orphan nuclear receptors, and 4) Antioxidant effect. Receptors associated with melatonin are as follows: 1) Melatonin receptor type 1a: MT1 (on cell membrane), 2) Melatonin receptor type 1b: MT2 (on cell membrane), 3) Melatonin receptor type 1c (found in fish, amphibians and birds), 4) Quinone reductase 2 enzyme (MT3 receptor, a detoxification enzyme), 5) RZR/RORα: Retinoid-related Orphan nuclear hormone receptor (with this receptor, melatonin binds to the transcription factors in nucleus), and 6) GPR50: X-linked Melatonin-related Orphan receptor (it is effective in binding of melatonin to MT1). Melatonin agonists such as ramelteon, agomelatine, circadin, TIK-301 and tasimelteon are introduced and side effects will be discussed. In conclusion, melatonin and related drugs is a new and promising era for medicine. Melatonin receptors and melatonin drugs will take attention with greater interest day by day in the future.   

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