Ramelteon

Ramelteon is a melatonin receptor agonist with both high affinity for melatonin MT1 and MT2 receptors, and lower selectivity for the MT3 receptor. Melatonin production is concurrent with nocturnal sleep, meaning that an increase in melatonin levels is related to the onset of self-reported sleepiness and an increase in sleep propensity. MT1 receptors are believed to be responsible for regulation of sleepiness and facilitation of sleep onset, and MT2 receptors are believed to mediate phase-shifting effects of melatonin on the circadian rhythm. While MT1 and MT2 receptors are associated with the sleep-wake cycle, MT3 has a completely different profile, and therefore is not likely to be involved in the sleep-wake cycle. Remelteon has no appreciable affinity for the gamma-aminobutyric acid (GABA) receptor complex or receptors that bind neuropeptides, cytokines, serotonin, dopamine, norepinephrine, acetylcholine, or opiates.