The opiate receptor: a model explaining structure-activity relationships of opiate agonists and antagonists.

Abstract
A model of the opiate receptor was proposed which explained the unique potency of certain opiates such as etonitazene, fentanyl, phenazocine and oripavines, the role of N-allyl substituents in conferring antagonist properties and chemical features that afford pure antagonists. The model indicated molecular mechanisms for interconversion of the opiate receptor between respective states that bind agonists or antagonists with high affinity.