title: A method for site selectivity analysis applied to opiate receptors.
abstract: A method has been developed to determine whether or not a receptor system consists of several sites with different binding specificity. Several radioactive indicator drugs are used in solutions of identical chemical composition. Homogeneity of the receptor system is tested graphically. We have applied the method to a study of opiate receptors. It appeared that there were at least two different binding sites. Several different competitors with various characteristics have been tested against three indicator solutions with radioactive dihydromorphine, naloxone and naltrexone respectively. Three different classes of opiates were observed in the system, morphine-like, naltrexone-like and an intermediate group. A morphine-like substance shows high selectivity for one of the sites while naltrexone-like compounds show practically no discrimination between the sites and a group of partial agonists such as nalorphine is intermediate.
mesh_terms: D000818:Animals; D066298:In Vitro Techniques; D009022:Morphine Derivatives / Q000494:pharmacology; D009270:Naloxone / Q000494:pharmacology; D009271:Naltrexone / Q000494:pharmacology; D051381:Rats; D011957:Receptors, Opioid / Q000187:drug effects*
chemical_list: D009022:Morphine Derivatives; D011957:Receptors, Opioid; D009270:Naloxone; D009271:Naltrexone