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Orexins (also called hypocretins) are hypothalamic peptides that promote arousal, attention, wakefulness, and behavioral activity. This manufacturer-sponsored study examined the impact of ACT-078573, a selective competitive antagonist of two orexin receptors, on sleep in animals and humans.
When administered to dogs and rats during normal wake times, ACT-078573 reduced alertness and activity compared with vehicle, without producing cataplexy or sleep attacks or altering other functions (e.g., temperature regulation). In rats, the compound increased time spent in rapid eye movement sleep and non-REM sleep, whereas the selective benzodiazepine receptor agonist zolpidem increased non-REM but decreased REM sleep. Dogs also showed indicators of i…