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. Widely expressed. Isoform 2 not detected in skeletal muscle and kidney. The N-terminal region is required for orexin signaling. Belongs to the G-protein coupled receptor 1 family.