= Opioid receptor
An <opioid receptor> is a <G protein-coupled receptor> recognizing opioid <ligands>, including endogenous <peptides> and exogenous <drugs>. Major <receptor> classes differ in distribution and <ligand> responses. Their signalling commonly engages inhibitory G <proteins>, linking <receptor> activation to changes in cyclic-AMP production and ion-channel activity. <Molecular Biology of the Cell, 4th edition by Bruce Alberts and others>[Chapter 15, G-protein-linked receptors and regulation of adenylyl cyclase and ion channels]{ref}
The same bound <ligand> need not produce identical effects in every assay. <Receptor> abundance, coupling efficiency and downstream amplification affect observed efficacy. Experiments comparing candidate opioid agonists showed why low intrinsic G-protein efficacy can help explain apparently favourable signalling profiles, rather than assuming that every difference establishes a uniquely selective pathway. <Low intrinsic efficacy for G protein activation can explain the improved side effect profiles of new opioid agonists by Alexander Gillis and others>[2020, abstract: efficacy and interpretation of agonist signalling profiles]{ref}
Back to article page
