Melatonin receptor type 1A (MT1) and Melatonin receptor type 1B (MT2) (MT1 (for type 1A), MT2 (for 1B))

Melatonin receptor type 1A (MT1) and Melatonin receptor type 1B (MT2) are high-affinity G protein-coupled receptors primarily responsible for mediating the physiological effects of melatonin, a neurohormone secreted by the pineal gland. These receptors are expressed throughout the brain (notably in the suprachiasmatic nucleus) and peripheral tissues, where they play critical roles in the regulation of circadian rhythms, sleep, and mood. MT1 and MT2 subtypes possess highly similar overall structures but have distinct tissue distributions and functional roles: MT1 is primarily implicated in promoting sleep and modulating REM phases, while MT2 is associated with phase shifting of circadian rhythms and has been genetically linked to type 2 diabetes risk. Drugs targeting these receptors are used for treatment of insomnia, circadian rhythm and mood disorders, and as research tools for chronobiology, with efforts ongoing to develop more subtype-selective therapeutics

Other names

Mel1AMTNR1AMel1BMTNR1BMelatonin receptors

Agonists bind to MT1 and/or MT2 receptors to activate downstream signaling (e.g., inhibit adenylate cyclase via Gi/Go, leading to reduced cAMP) Modulation of sleep–wake cycles, circadian rhythms, and mood via GPCR signaling