Related Experiment Video
Updated: Sep 1, 2026

Quantifying Agonist Activity at G Protein-coupled Receptors
Published on: December 26, 2011
Physical separation of the agonist and antagonist forms of a mu opiate receptor?
Abstract:
The rabbit cerebellum contains up to 80% of mu opiate binding sites (J.C. Meunier, Life Sci. 31, 1327-1330 (1982) ). A crude membrane fraction derived therefrom was labelled either with the opiate agonist: 3H-etorphine or with the opiate antagonist: 3H-diprenorphine, and solubilized with digitonin. Centrifugation of the soluble extracts in linear sucrose gradients reveals that bound 3H-etorphine sediments faster than does bound 3H-diprenorphine: 12S vs 10S. The 3H-etorphine macromolecular complex (12S) is virtually absent in extracts of membranes that have been labelled in the presence of 120 mM NaCl or of 50 microM Gpp(NH)p (guanyl-5'-yl imidodiphosphate). Under the same conditions, recovery of 3H-diprenorphine in bound (10S) form is either not affected (Gpp(NH)p) or substantially increased (NaCl). These data are consistent with the notion that cerebellar mu opiate receptors may exist under physically separable agonist and antagonist states.
Related Concept Videos
Drug-Receptor Interactions
Several parameters, such as the drug's affinity for its receptor and its efficacy, which is its ability to activate the receptor, determine the drug's effect on the tissue.
Drug-Receptor Interaction: Agonist
Agonists can bind to receptors in different ways. Some agonists bind directly to the receptor's active site, mimicking the endogenous ligand's action.
Drug-Receptor Interaction: Antagonist
Antagonists can be classified as competitive or noncompetitive based on their...
Combined Effects of Drugs: Antagonism
The most common type is receptor antagonism, where one drug acts as an antagonist to block the effects of another drug by...
The Two-State Receptor Model
The binding affinity of a drug determines its interaction with one...
Opioid Receptors: Overview

