US -endorphin-(1-27) is a naturally occurring antagonist to etorphine-induced analgesia

Journal Article · Wed May 01 00:00:00 EDT 1985 · Proc. Natl. Acad. Sci. U.S.A.; (United States)

DOI:https://doi.org/10.1073/pnas.82.10.3178· OSTI ID:6334305

Nicolas, P; Li, C H

The potent opioid peptide US -endorphin is found in the brain and pituitary with two related fragments, US -endorphin-(1-27) and US -endorphin-(1-26). The fragments, retain substantial opioid-receptor binding activity but are virtually inactive analgesically. US -Endorphin-(1-27) inhibits US -endorphin-induced and etorphine-induced analgesia when coinjected intracerebroventricularly into mice. Antagonism by competition at the same site(s) is suggested from parallel shifts of the dose-response curves of etorphine or US -endorphin in the presence of US -endorphin-(1-27). Its potency is 4-5 times greater than that of the opiate antagonist naloxone. US -Endorphin-(1-26) does not antagonize the antinociceptive action of etorphine or US -endorphin in doses up to 500 pmol per animal.

• Research Organization: Univ. of California, San Francisco, CA (United States)
• OSTI ID: 6334305
• Journal Information: Proc. Natl. Acad. Sci. U.S.A.; (United States), Vol. 82:10
• Country of Publication: United States
• Language: English

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