Dynorphinergic pathways of Leu-enkephalin production in the rat brain.
Leu-Enkephalin (LE) is an endogenous opioid peptide that can arise from two distinct precursors: proenkephalin and prodynorphin. Experiments were designed to differentiate LE derived from proenkephalin versus that derived from prodynorphin. The most dense collections of dynorphin-positive fibers and terminals are in the substantia nigra and posterior pituitary, areas rich in dynorphin-related peptides. The concentration of LE in these regions is significantly higher than that of ME-Arg-Gly-Leu; the ratio of LE to ME-Arg-Gly-Leu is therefore greater than that found in the proenkephalin precursor, which is unity. Globus pallidus deafferentation resulted in a significant decrease of dynorphin B and LE, but not ME-Arg-Gly-Leu, in the substantia nigra. Mild intermittent foot shock (0.2 mA, 20 min) causes a significant increase of dynorphin B and LE in the substantia nigra, but has no effect on ME-Arg-Gly-Leu concentrations. Thus, in the substantia nigra LE may be derived primarily from prodynorphin. Likewise, in the posterior pituitary, osmotic stimulus (e.g., 2% NaCl as drinking fluid) causes marked depletion in dynorphin and LE but has no effect on ME levels suggesting that in the posterior pituitary LE is derived primarily from dynorphin.
Zamir
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Quirion
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D000818:Animals; D003342:Corpus Striatum / Q000378:metabolism*; D004399:Dynorphins / Q000378:metabolism*; D004743:Enkephalin, Leucine / Q000096:biosynthesis*; D004745:Enkephalins / Q000378:metabolism; D008297:Male; D009434:Neural Pathways / Q000378:metabolism; D010904:Pituitary Gland, Posterior / Q000378:metabolism*; D011498:Protein Precursors / Q000378:metabolism; D051381:Rats; D011919:Rats, Inbred Strains; D013378:Substantia Nigra / Q000378:metabolism*
D004745:Enkephalins; D011498:Protein Precursors; C029992:proenkephalin; D004743:Enkephalin, Leucine; D004399:Dynorphins; C033660:preproenkephalin