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δ-Opioid receptor: the third extracellular loop determines naltrindole selectivity

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Abstract

Human δ/μ-opioid receptor chimeras were constructed to determine the role of the second and third extracellular loops in alkaloid ligand selectivity. Exchanging the third extracellular loop of the δ-opioid receptor with that of the μ-opioid receptor dramatically decreased the affinity of naltrindole, but not that of morphine. The results suggest that different domains of the opioid receptor are involved in the binding of naltrindole and morphine.

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