G protein-coupled receptor that binds the neuropeptide orexin-A with high affinity, and orexin-B with lower affinity, two peptides derived from a common precursor, prepro-orexin (PubMed:32669442, PubMed:9491897). Its activity is mediated via a G(q)- protein-coupled pathway, which activates the phosphatidylinositol- calcium second messenger system in response to orexin-A binding (PubMed:32669442). In addition to G(q)-mediated signaling, orexin-A stimulation also promotes beta-arrestin recruitment, leading to receptor internalization (PubMed:15683363, PubMed:32669442). Plays a significant role in the regulation of food intake (By similarity). {ECO:0000250|UniProtKB:P56718, ECO:0000269|PubMed:15683363, ECO:0000269|PubMed:32669442, ECO:0000269|PubMed:9491897}. This is the function of ENSG00000121764 (HCRTR1, hypocretin receptor 1).