Regional interactions of opioid peptides at μ and δ sites in rat brain |
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Authors: | William A Hewlett Jack D Barchas |
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Institution: | Nancy Pritzker Laboratory of Behavioral Neurochemistry Department of Psychiatry and Behavioral Sciences, Stanford University School of Medicine, Stanford, CA 94305, USA |
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Abstract: | Opiate binding sites in five brain regions were labeled with the μ and δ markers, 3H-morphine and 3H-D-Ala2,D-leu5]enkephalin, respectively. The highest densities of both 3H-morphine and 3H-DADLE labeled sites are found in striatum and frontal cortex. Hypothalamus and midbrain contain predominantly 3H-morphine labeled sites. The selectivity of the opioid peptides D-Ala2,D-leu5]enkephalin, β-endorphin and dynorphin(1–13) for the two opiate sites was investigated by comparing the potency of these unlabeled compounds against the μ and δ markers in different brain regions. This determination has the effect of controlling for the breakdown of peptides within each region. While the enkephalin analogue shows a preference for the δ binding site and β-endorphin is more nearly equipotent towards the two binding sites, dynorphin(1–13) shows a high affinity and selective preference for the μ binding site over the δ site. The potency of the opioid peptides in displacing the μ and δ markers varies from region to region according to the relative densities of the two opiate binding site populations. |
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Keywords: | Multiple opiate receptors Rat brain regions 3H-morphine binding 3H-DADLE binding Dynorphin selectivity β-Endorphin selectivity |
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