Melatonin is a naturally occurring compound found in animals, plants, and microbes [[cite:PUB00066873], [cite:PUB00066874]]. In animals melatonin is secreted by the pineal gland during darkness [[cite:PUB00066875], [cite:PUB00066876]]. It regulates a variety of neuroendocrine functions and is thought to play an essential role in circadian rhythms [[cite:PUB00066877]]. Drugs that modify the action of melatonin, and hence influence circadian cycles, are of clinical interest for example, in the treatment of jet-lag [[cite:PUB00066878]].
\r\nMany of the biological effects of melatonin are produced through the activation of melatonin receptors [[cite:PUB00066879]], which are members of rhodopsin-like G protein-coupled receptor family. There are three melatonin receptor subtypes. Melatonin receptor type 1A and melatonin receptor type 1B are present in humans and other mammals [[cite:PUB00066880]] while melatonin receptor type 1C has been identified in amphibia and birds [[cite:PUB00066881]]. There is also a closely-related orphan receptor, termed melatonin-related receptor type 1X (also known as GPR50) [[cite:PUB00066882]], is yet to achieve receptor status from the International Union of Basic and Clinical Pharmacology (IUPHAR), since a robust response mediated via the protein has not been reported in the literature. Melatonin receptor type 1C receptors are 80% identical and are distinct from 1A and 1B subtypes. Similar ligand binding and functional characteristics are observed in expressed 1A and 1C receptors. The melatonin receptors inhibit adenylyl cyclase via a pertussis-toxin-sensitive G-protein, probably of the Gi/Go class.
","llm":false,"checked":false,"updated":false},{"text":"This entry represents the melatonin receptor family.
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