title: Opiate agonists and antagonists discriminated by receptor binding in brain.
abstract: Receptor binding of opiate agonists and antagonists can be differentiated in vivo and in vitro. Administration of either rapidly elevates stereospecific [(3)H]dihydromorphine binding to mouse brain extracts by 40 to 100 percent, but antagonists are 10 to 1000 times more potent than agonists; as little as 0.02 milligram of naloxone per kilogram of body weight significantly enhances opiate receptor binding. Sodium enhances antagonist binding in vitro but decreases agonist binding, a qualitative difference that may be relevant to the divergent pharmacological properties of opiate agonists and antagonists.
mesh_terms: D000700:Analgesics / Q000494:pharmacology*; D000818:Animals; D001667:Binding, Competitive; D001921:Brain / Q000378:metabolism*; D004091:Hydromorphone / Q000378:metabolism*; D066298:In Vitro Techniques; D007977:Levallorphan / Q000494:pharmacology; D007981:Levorphanol / Q000494:pharmacology; D051379:Mice; D009020:Morphine / Q000494:pharmacology; D009269:Nalorphine / Q000494:pharmacology; D009270:Naloxone / Q000378:metabolism / Q000494:pharmacology; D009292:Narcotic Antagonists / Q000494:pharmacology*; D010111:Oxymorphone / Q000494:pharmacology; D011955:Receptors, Drug; D012964:Sodium / Q000494:pharmacology; D014316:Tritium
chemical_list: D000700:Analgesics; D009292:Narcotic Antagonists; D011955:Receptors, Drug; D014316:Tritium; D007981:Levorphanol; D007977:Levallorphan; D009270:Naloxone; D009020:Morphine; D012964:Sodium; D010111:Oxymorphone; D004091:Hydromorphone; D009269:Nalorphine