Opiate Agonists and Antagonists Discriminated by Receptor Binding in Brain

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Science  28 Dec 1973:
Vol. 182, Issue 4119, pp. 1359-1361
DOI: 10.1126/science.182.4119.1359


Receptor binding of opiate agonists and antagonists can be differentiated in vivo and in vitro. Administration of either rapidly elevates stereospecific [3H]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.

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