Mast cell-specific receptor for basic secretagogues, i.e. cationic amphiphilic drugs, as well as endo- or exogenous peptides, consisting of a basic head group and a hydrophobic core. Recognizes and binds small molecules containing a cyclized tetrahydroisoquinoline (THIQ), such as non-steroidal neuromuscular blocking drugs (NMBDs), including tubocurarine and atracurium. In response to these compounds, mediates pseudo-allergic reactions characterized by histamine release, inflammation and airway contraction (PubMed:25517090). Mast cell-specific. No visible phenotype in normal conditions. Absence of pseudo-allergic reactions in response to small-molecule therapeutic drugs: secretagogue-induced histamine release, inflammation and airway contraction are abolished. Belongs to the G-protein coupled receptor 1 family. Mas subfamily. In spite of its official gene name, this protein may be the functional ortholog of human MRGPRX2, in terms of expression pattern and pharmacology.