Time course and magnitude of tolerance to the analgesic effects of systemic morphine in amphibians

Craig W. Stevens, Kenan Kirkendall

Research output: Contribution to journalArticle

20 Citations (Scopus)

Abstract

The systemic administration of morphine (100 nmol/g, s.c.) produced a significant and long-lasting analgesia (up to 8 h) in the Northern grass frog, Rana pipiens. Daily bolus injections of the same dose of morphine or saline for one week resulted in a significant analgesia for 3 days in the morphine group, which fell to levels indistinguishable from the saline-treated controls on days 4 through 7. In separate experiments, animals were treated identically with morphine or saline but were not tested daily for pain thresholds. In these animals, administration of a range of morphine doses on day 8 yielded dose-response curves significantly-shifted rightward by a factor of 3.3 in the morphine-treated group compared to the saline-injected controls. These studies are the first to show the time course of tolerance development and the magnitude of morphine tolerance in a non-mammalian vertebrate species.

Original languageEnglish
Pages (from-to)PL-111-PL-116
JournalLife Sciences
Volume52
Issue number15
DOIs
StatePublished - 1 Jan 1993

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Amphibians
Morphine
Analgesics
Analgesia
Animals
Rana pipiens
Pain Threshold
Poaceae
Anura
Vertebrates
Injections
Experiments

Cite this

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abstract = "The systemic administration of morphine (100 nmol/g, s.c.) produced a significant and long-lasting analgesia (up to 8 h) in the Northern grass frog, Rana pipiens. Daily bolus injections of the same dose of morphine or saline for one week resulted in a significant analgesia for 3 days in the morphine group, which fell to levels indistinguishable from the saline-treated controls on days 4 through 7. In separate experiments, animals were treated identically with morphine or saline but were not tested daily for pain thresholds. In these animals, administration of a range of morphine doses on day 8 yielded dose-response curves significantly-shifted rightward by a factor of 3.3 in the morphine-treated group compared to the saline-injected controls. These studies are the first to show the time course of tolerance development and the magnitude of morphine tolerance in a non-mammalian vertebrate species.",
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Time course and magnitude of tolerance to the analgesic effects of systemic morphine in amphibians. / Stevens, Craig W.; Kirkendall, Kenan.

In: Life Sciences, Vol. 52, No. 15, 01.01.1993, p. PL-111-PL-116.

Research output: Contribution to journalArticle

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