What is MT1 and MT2?
Melatonin activates two high-affinity G protein-coupled receptors, termed MT1 and MT2, to exert beneficial actions in sleep and circadian abnormality, mood disorders, learning and memory, neuroprotection, drug abuse, and cancer. Melatonin receptor activation decreases neuronal firing through activation of the MT1 receptor in the SCN and areas of the limbic system, which may mediate the sleep-promoting properties of melatonin (9, 14).