Distinct effects of orexin receptor antagonist and GABAA agonist on sleep and physical/cognitive functions after forced awakening Jaehoon Seola,b,1, Yuya Fujiib,1, Insung Parka, Yoko Suzukia, Fusae Kawanaa, Katsuhiko Yajimac, Shoji Fukusumia, Tomohiro Okurad, Makoto Satoha, Kumpei Tokuyamaa, Toshio Kokuboa, and Masashi Yanagisawaa,e,f,g,2 aInternational Institute for Integrative Sleep Medicine, University of Tsukuba, 305-8575 Tsukuba, Ibaraki, Japan; bPhysical Education, Health, and Sport Sciences, University of Tsukuba, 305-8574 Tsukuba, Ibaraki, Japan; cFaculty of Health and Nutrition, Tokyo Seiei College, 124-8530 Tokyo, Japan; dFaculty of Health and Sport Sciences, University of Tsukuba, 305-8574 Tsukuba, Ibaraki, Japan; eLife Science Center for Survival Dynamics (TARA), University of Tsukuba, Ibaraki, 305-8577, Japan; fR&D Center for Frontiers of Mirai in Policy and Technology (F-MIRAI), University of Tsukuba, Ibaraki, 305-8575, Japan; and gDepartment of Molecular Genetics, University of Texas Southwestern Medical Center, Dallas, TX 75390 Contributed by Masashi Yanagisawa, September 14, 2019 (sent for review April 29, 2019; reviewed by Seiji Nishino and Kenneth P. Wright, Jr.) The majority of patients with insomnia are treated with hypnotic Suvorexant is a recently approved orexin receptor antagonist agents. In the present study, we evaluated the side-effect profile of representing an alternative mechanistic approach for the treat- γ an orexin receptor antagonist and -aminobutyric acid A (GABAA)re- ment of insomnia, which specifically inhibits the orexin-mediated ceptor agonist on physical/cognitive functions upon forced awak- wake-promoting system (12). Unlike GABAA agonists, orexin ening. This double-blind, randomized, placebo-controlled, cross-over receptor antagonists promote both NREM and rapid eye move- study was conducted on 30 healthy male subjects. Fifteen mi- ment (REM) sleep, do not disrupt sleep-stage-specific quantitative nutes before bedtime, the subjects took a pill of suvorexant (20 mg), EEG spectral profiles, and allow somnolence indistinct from brotizolam (0.25 mg), or placebo and were forced awake 90 min there- normal sleep (12). In animal studies, sleep induced by an orexin after. Physical- and cognitive-function tests were performed be- receptor antagonist did not impair the ability to selectively re- fore taking the pill, after forced awakening, and the next morning. spond and arouse to emotionally salient auditory stimuli, similar to Polysomnographic recordings revealed that the efficacies of the hyp- natural sleep (13, 14). Interestingly, after awakening, the animals PHARMACOLOGY notic agents in prolonging total sleep time (∼30 min) and increasing sleep efficiency (∼6%) were comparable. When the subjects were returned to sleep in a dose-proportional manner. allowed to go back to sleep after the forced awakening, the sleep The potential side effects of GABAA agonists include impaired latency was shorter under the influence of hypnotic agents (∼2min) cognitive and physical functions upon awakening from sleep (15, compared to the placebo trial (24 min), and the rapid eye movement 16). Animal studies have suggested distinct effects of GABAA ag- latency was significantly shorter under suvorexant (98.8, 81.7, and 48.8 onists and orexin receptor antagonists on motor and cognitive min for placebo, brotizolam, and suvorexant, respectively). Although functions (17–19). Motor coordination assessed 30 min after the brotizolam significantly impaired the overall physical/cognitive perfor- administration of hypnotic drugs was impaired by the GABAA mance (sum of z score) compared with placebo upon forced awak- agonists zolpidem, eszopiclone, and diazepam in a dose-dependent ening, there was no significant difference in the total z score of performance between suvorexant and placebo. Notably, the score Significance for static balance with the eyes open was higher under suvorexant compared to brotizolam administration. The energy expenditure Insomnia is a common symptom representing an important was lower under suvorexant and brotizolam compared with the health burden. Widely prescribed hypnotic agents enhance the d = placebo. The effect size of brotizolam ( 0.24) to reduce the function of γ-aminobutyric acid (GABA), a major inhibitory d < energy expenditure was larger than that of suvorexant ( 0.01). neurotransmitter. The ability to arouse and respond to un- expected stimuli is a feature of normal sleep, and one of the hypnotics | benzodiazepines | Stroop color-word test | Purdue pegboard concerns of this class of hypnotic agents is that patients may test | body sway become physically and/or cognitively impaired while the drug is in effect. As a new approach for the treatment of insomnia, nsomnia is a common symptom in the general population, and orexin receptor antagonists have been recently approved, Ivarious studies worldwide have shown its prevalence in 10 to which specifically inhibit the orexin-mediated wake-promoting 30% of the population, some even as high as 50 to 60% (1–4). system, supposedly without affecting the whole brain. We Chronic insomnia occurs in 9 to 33% of the adult population (5, found that, compared with the GABA receptor agonist brotizolam, 6), and nearly half (45.6%) of the patients with insomnia take the orexin receptor antagonist suvorexant induced less impair- hypnotic agents (7). Currently, the most commonly prescribed ment in body balance after taking the medicine. hypnotic agents are γ-aminobutyric acid (GABA) agonists, which Author contributions: S.F., T.K., and M.Y. designed research; J.S., Y.F., I.P., Y.S., F.K., T.O., enhance the function of the major inhibitory neurotransmitter M.S., and K.T. performed research; J.S., Y.F., I.P., Y.S., F.K., K.Y., T.O., and K.T. analyzed data; and J.S., Y.F., K.T., and M.Y. wrote the paper. GABA by binding to the allosteric benzodiazepine site on GABAA receptors. Electroencephalographic (EEG) power spectral analyses Reviewers: S.N., Stanford University School of Medicine; and K.P.W., University of have revealed a decrease in low-frequency (0.25 to 7.02 Hz) activity Colorado Boulder. andanincreaseinhigh-frequencyactivity(14.04to21.84Hz)in The authors declare no competing interest. non-rapid eye movement (NREM) sleep with the administration of Published under the PNAS license. 1J.S. and Y.F. contributed equally to this work. these GABAA receptor agonists (8, 9). As a consequence of the 2To whom correspondence may be addressed. Email: yanagisawa.masa.fu@u. widespread expression of GABAA receptors in the central nervous tsukuba.ac.jp. system, GABAA receptor agonists can inhibit neurons throughout This article contains supporting information online at www.pnas.org/lookup/suppl/doi:10. the brain and spinal cord, including those not involved in the in- 1073/pnas.1907354116/-/DCSupplemental. duction and maintenance of sleep (10, 11). First published November 11, 2019. www.pnas.org/cgi/doi/10.1073/pnas.1907354116 PNAS | November 26, 2019 | vol. 116 | no. 48 | 24353–24358 Downloaded by guest on October 1, 2021 manner, but not following the administration of the orexin receptor N3 N2 N1 R W antagonist DORA-22 (17). However, the effect of orexin receptor 100% antagonists on human cognitive and physical functions upon tnaxerovuS 80% awakening from sleep remains untested. In addition, orexin re- 60% ceptor antagonists may modulate energy metabolism during sleep 40% (20), as orexin infusion into the hypothalamus increases the oxy- 20% Post-test gen consumption of freely behaving and anesthetized rats (21, 22). 0% 100% Moreover, orexin receptor antagonists and GABAA agonists could 80% modify energy metabolism during sleeping through their effects on malozitorB the sleep architecture, as the sleeping energy expenditure is re- 60% lated to the sleep stages (23). The primary objective of the present 40% study was to compare the pharmacological effects of an orexin 20% Post-test receptor antagonist and a GABA agonist on physical and cog- 0% A 100% nitive functions upon forced awakening when the drug effect was 80% maximal. We also assessed the effects of hypnotic agents on the obecalP metabolic rate while sleeping. 60% 40% Results 20% Post-test Subject Characteristics. The characteristics of the subjects are 0% presented in SI Appendix, Table S1. All subjects fulfilled the inclusion/exclusion criteria (SI Appendix, SI Materials and Methods). The time in bed, total sleep time, sleep latency, and sleep Fig. 1. Cumulative display of sleep architecture in all 30 subjects. The per- efficiency of the adaptation night were 515 min, 460.4 ± 46.0 centage of subjects in each sleep stage is shown. The subjects were forced min, 6.0 ± 7.5 min, and 89.4 ± 8.9%, respectively. Due to some awake at 00:15 and went back to sleep at 00:40. technical problems, there were missing data for 1 Stroop color-word test, 1 eyes-opened body-sway test, and 2 indirect calorimetry measurements. by brotizolam. A substantial decrease in wake was observed under both hypnotic agents during the 1st quarter of sleep. An Sleep Parameters. The total sleep time during the total time in increase in stage R by suvorexant was also observed during the bed was increased by brotizolam and suvorexant compared with 3rd quarter, and an increase in stage N2 by brotizolam was ob- the placebo (Table 1). Brotizolam and suvorexant decreased the served during the 2nd quarter of sleep time (SI Appendix, Table awake time and increased sleep efficiency. Suvorexant increased S5). When the subjects were allowed to go back to sleep after stage REM (R) compared with brotizolam and placebo. Brotizolam forced awakening, suvorexant significantly decreased the REM increased stage NREM 2 (N2) compared with suvorexant and latency and prolonged stage R compared with the other 2 trials. placebo (Fig. 1 and Table 1). In 40% of the subjects, stage R occurred with a short REM la- When the sleep architecture was separately analyzed before and tency (<15 min) under the influence of suvorexant (SI Appendix, after forced awakening, there were no statistically significant dif- Table S4 and Fig.