Demonstration of two classes of opiate binding sites in the nervous tissue of the marine mollusc Mytilus edulis. Positive homotropic cooperativity of lower affinity binding sites.

Animals Binding Sites Binding, Competitive Bivalvia/metabolism Cell Membrane/metabolism D-Ala(2),MePhe(4),Met(0)-ol-enkephalin Endorphins/metabolism Enkephalin, Methionine/analogs & derivatives,metabolism Etorphine/metabolism Ganglia/metabolism Kinetics Levallorphan/metabolism Morphinans/metabolism Receptors, Opioid/metabolism

Endorphins Morphinans Receptors, Opioid Levallorphan Etorphine Enkephalin, Methionine D-Ala(2),MePhe(4),Met(0)-ol-enkephalin