Nonselective, high-affinity receptor for both orexin-A and orexin-B neuropeptides. Triggers an increase in cytoplasmic Ca(2+) levels in response to orexin-A binding. The N-terminal region is required for orexin signaling. Defects in HCRTR2 are a cause of an autosomal recessive form of narcolepsy, observed in labradors, dobermans and dachshunds. Narcolepsy is a neurological sleep disorder affecting animals and humans, characterized by excessive daytime sleepiness, sleep fragmentation, symptoms of abnormal rapid-eye-movement (REM) sleep, such as cataplexy, hypnagogic hallucinations, and sleep paralysis. Cataplexy is a sudden loss of muscle tone triggered by emotions, which is the most valuable clinical feature used to diagnose narcolepsy. As in humans, most cases of canine narcolepsy are sporadic but an autosomal recessive form was also observed. Belongs to the G-protein coupled receptor 1 family.