The 'hot ligand' that was used in the binding assay that yielded the information about the ligand-receptor interaction. A 'hot ligand' is a modified (e.g. radioactive) ligand for a receptor that is used in binding assays to determine the affinity of another ligand. Activation threshold (e.g. of a voltage-gated ion channel). Dimension: voltage. Units: mV Half activation voltage (e.g. of a voltage-gated ion channel). Dimension: voltage. Units: mV The IUPHAR(international union of pharmacology) receptor code. Functional property.