Hydrodynamic properties of a [3H]etorphine macromolecular complex from the rat brain

In the central nervous system, opiates produce their various pharmacological effects primarily by interacting with stereospecific binding sites [l-3].These sites are presumably carried by membrane-bound opiate receptors which, as such, have not yet been unambig ously identified and, a fortiori, purified.A first step toward these major goals is to prove that macromolecular (?) species which bind opiates with high affmity and stereospecifically do exhibit well defined hydrodynamic properties in solution.A classical approach [4] makes use of highly selective, nearly irreversible radioactive ligands to label the receptor molecule(s).The resulting membrane-bound, radioactive complex is then solubilized with the appropriate chaotropic agent after which its hydrodynamic properties are analyzed by conventional techniques, namely gel filtration and ultracentrifugation