The Involvement of 5-HT 2A Receptor in the Regulation of Sleep and Wakefulness, and the Potential Therapeutic Use of Selective 5-HT 2A Receptor Antagonists and Inverse Agonists for the Treatment of an Insomnia Disorder

Several agents have been shown to improve sleep induction and/or maintenance in patients with primary or comorbid insomnia. These include benzodiazepine and non-benzodiazepine receptor allosteric modulators, melatonin and the melatonin receptor agonist ramelteon, low dose doxepin, and suvorexant. However, benzodiazepines induce a further reduction of N3 sleep [slow wave sleep (SWS) or delta sleep] and rapid-eye-movement sleep (REMS), whereas values corresponding to these variables remain decreased during non-benzodiazepine, melatonin, ramelteon or low-dose doxepin administration. By contrast, suvorexant increases REMS. There is evidence indicating that non-selective (ritanserin, ketanserin, sertindole, ICI-170809, ICI-169369, RP-62203, SR-46349B) and selective (volinanserin, pruvanserin, eplivanserin) 5-HT2A receptor antagonists, as well as 5-HT2A receptor inverse agonists (nelotanserin, pimavanserin) increase SWS in laboratory animals and N3 sleep in subjects with normal sleep and/or patients with an insomnia disorder. Thus, the association of a selective 5-HT2A receptor antagonist or a 5-HT2A receptor inverse agonist with a hypnotic drug could be a valid alternative to normalize N3 sleep in patients with an insomnia complaint.