[Receptor occupation and pharmacological activity as demonstrated on opiates (author's transl)].

The availability of highly radioactively labelled opiates with high receptor affinity has made it possible to identify and characterize opiate receptors in vitro as well as in vivo. These investigations revealed that the affinity of the compounds to the receptor decides about the pharmacological potency of the compounds. The differing action of opiate agonists and antagonists are explained by an allosteric receptor model. In vivo experiments showed that the dose range at which opiates induce specific pharmacological actions is identical with those doses at which increasing and finally complete receptor occupancy is obtained. Toxicological aspects of receptor occupation are discussed.