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J Comp Neurol. 2012 May 1;520(7):1547-61. doi: 10.1002/cne.22811.

Localization of endogenous morphine-like compounds in the mouse spinal cord.

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Nociception and Pain Department, Centre National de la Recherche Scientifique and University of Strasbourg, Institut des Neurosciences Cellulaires et Intégratives, F-67084 Strasbourg, France.


Morphine, codeine, morphine-6-glucuronide, and morphine-3-glucuronide are synthesized de novo in mammalian cells and in the central nervous system. Knowledge on endogenous morphine-like compound distribution in the adult mouse brain has been recently improved, and new hypotheses have been suggested about the potential implications in brain physiology. Endogenous morphine-like compounds have been shown to be synthesized in the spinal cord, but their localization is unknown. Here we describe the distribution of endogenous morphine-like compounds (morphine and/or its glucuronides and/or codeine) in the adult mouse spinal cord using a well-validated antibody. By using different microscopy approaches, we found the presence of morphine, codeine, or morphine glucuronides in γ-aminobutyric acid (GABA)-ergic neurons and astrocytes of the spinal cord. Whereas GABAergic neurons containing endogenous morphine-like compounds were located primarily in the ventral horn, astrocytes that were labeled for morphine-like compounds were found throughout the gray matter and the white matter. Our study demonstrates the possibility that endogenous morphine-like compounds in the central nervous system have other functions beyond their analgesic functions.

[Indexed for MEDLINE]

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