High Quality Content by WIKIPEDIA articles! Receptor theory is the application of receptor models to explain drug behaviour. Pharmacological receptor models preceded accurate knowledge of receptors by many years.John Newport Langley and Paul Ehrlich introduced the concept of a receptor that would mediate drug action at the beginning of the 20th century. A J Clark was the first to quantify drug-induced biological responses (using an equation described firstly by A V Hill in 1909 and then in 1910) and propose a model to explain drug-mediated receptor activation. So far, nearly all of the quantitative theoretical modelling of receptor function has centred on ligand-gated ion channels and GPCRs.