β Endorphin: cross tolerance to and cross physical dependence on morphine

L. F. Tseng, H. H. Loh, C. H. Li

Research output: Contribution to journalArticlepeer-review

63 Scopus citations

Abstract

The effects of β endorphin on the antinociceptive responses and abrupt withdrawal jumping in morphine dependent mice were studied. Mice were rendered morphine dependent by implantation of a morphine pellet (75 mg base) for 3 days. The analgesic response to β endorphin decreased after morphine pellet implantation, as evidenced by an eight fold increase in the median antinociceptive dose. A similar increase in the median antinociceptive dose of morphine was found. In small doses (0.09 - 0.17 μg per mouse ), β endorphin suppressed abrupt withdrawal jumping. Met enkephalin, even in high doses (200 μg per mouse), did not suppress abrupt withdrawal jumping.

Original languageEnglish (US)
Pages (from-to)4187-4189
Number of pages3
JournalProceedings of the National Academy of Sciences of the United States of America
Volume73
Issue number11
DOIs
StatePublished - 1976

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