This is a receptor for the tachykinin neuropeptide substance P. It is probably associated with G proteins that activate a phosphatidylinositol-calcium second messenger system. The rank order of affinity of this receptor to tachykinins is: substance P > substance K > neuromedin-K. Interacts with ARRB1. In contrast to Fong et al. data (PubMed:1310144), isoform 2 is not detected by PCR in any of 24 human tissues examined including the placenta (PubMed:11864635). Belongs to the G-protein coupled receptor 1 family. Tachykinin entry