Ramelteon is a MT1/MT2 agonist marketed for insomnia, and tasimelteon, another MT1/MT2 agonist, is marketed for non-24-hour sleep-wake disorder. These agents help to improve what process of sleep?

A. Sleep maintenance: Sleep maintenance refers to staying asleep through the night. Melatonin receptor agonists primarily facilitate the initiation of sleep rather than preventing nighttime awakenings. B. Sleep onset: Ramelteon and tasimelteon are MT1/MT2 receptor agonists that mimic endogenous melatonin. By acting on these receptors in the suprachiasmatic nucleus, they help regulate circadian rhythms and promote the initiation of sleep, improving sleep onset latency. C. Sleep efficiency: Sleep efficiency measures the proportion of time in bed spent asleep. While improved sleep onset may indirectly enhance efficiency, these agents specifically target falling asleep rather than overall sleep consolidation. D. Deep Wave Sleep: Deep wave sleep (slow-wave sleep) is primarily regulated by homeostatic sleep pressure and GABAergic mechanisms, not directly by melatonin receptor agonists.