Morphine in cow and human milk: could dietary morphine constitute a ligand for specific morphine (mu) receptors?

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Science  28 Aug 1981:
Vol. 213, Issue 4511, pp. 1010-1012
DOI: 10.1126/science.6267691


Morphine has been found in cow and human milk at concentrations of 200 to 500 nanograms per liter. Multistep purification yields a material that has immunological, biological, pharmacological, and chemical properties identical to those of morphine. Similar morphine-like material, which has been tentatively identified in some common plant sources, may be a ubiquitous dietary constituent and a possible source for the material in milk. Since morphine (mu) receptors have a low affinity for enkephalins, and since morphine-like materials have been described in brain and intestine, it is possible that morphine in food may be the source of this material and a normal ligand specific for mu receptors.