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. Belongs to the G-protein coupled receptor 1 family. Mas subfamily.