Orphan receptor activated by a subset of RFamide-family neuropeptides such as FLRF-amide and FMRF-amide. Mediates its action by association with G proteins that activate a phosphatidylinositol-calcium second messenger system. Its effect is mediated by G(q) and G(11) proteins. May regulate the function of nociceptive neurons by modulation of pain perception. Expressed in a subset of sensory neurons that includes nociceptors. Expressed in the subclass of non-peptidergic sensory neurons that are IB4(+) and VR1(-). Belongs to the G-protein coupled receptor 1 family. Mas subfamily.