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Study · Animal study (in vivo) · mouse · 1981

9 results

Facilitation of morphine-induced tolerance and physical dependence by prolyl-leucyl-glycinamide.

Contreras PC, Takemori AE

European journal of pharmacology1 May 1981Cited by 11 (Europe PMC)

PMID6113968 (opens in a new tab)DOI10.1016/0014-2999(81)90028-5 (opens in a new tab)PepBankPUB-06113968
Publisher pagePubMedAsk about this study
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Summary

The text of this summary is not shown here, because the article license does not allow reuse. Read it at the source (opens in a new tab)

Text rights: Publisher copyright. Results still quote short attributed sentences.

Results from this study9

9 results from studies that gave the peptide. No result from this study comes from people.

  1. 01AnimalAnimal study (in vivo)Efficacy outcome

    In mice, morphine pretreatment decreased subsequent morphine analgesia after PLG pretreatment, whereas it did not after saline pretreatment.

    In plain wordsIn mice, morphine pretreatment reduced later morphine pain relief after PLG pretreatment, but not after saline pretreatment.

    Peptide
    MIF-1 (Pro-Leu-Gly-NH2)
    Outcome
    DecreaseAnalgesic response after morphine pretreatment
    Study

    mousen: not reported in source

    Morphine tolerance and dependence
    Comparator
    Saline pretreatment
    Outcome group
    Drug tolerance · Nervous system and cognition
    Studied dose
    Dose not stated

    Source sentences

    Summary
    The pretreatment of mice with 30 mg/kg morphine s.c. did not alter the analgesic effect of morphine in mice pretreated with saline but decreased the analgesic effect of morphine in mice pretreated with prolyl-leucyl-glycinamide (PLG).
  2. 02AnimalAnimal study (in vivo)Efficacy outcome

    In morphine-pretreated mice, naloxone potency was twofold greater with PLG treatment than in controls.

    In plain wordsIn morphine-pretreated mice, naloxone was twice as potent with PLG treatment as in controls.

    Peptide
    MIF-1 (Pro-Leu-Gly-NH2)
    Outcome
    IncreaseNaloxone potency after morphine pretreatment
    Study

    mousen: not reported in source

    Morphine tolerance and dependence
    Comparator
    Control mice
    Outcome group
    Drug tolerance · Nervous system and cognition
    Studied dose
    Dose not stated

    Measurements

    Naloxone potency ratio
    2 fold
    PLG versus control

    Source sentences

    Summary
    The naloxone potency of PLG-treated mice was 2-fold greater than that of control mice.
    2 context sentences
    Summary · context
    Tolerance was evaluated by the effect of PLG on morphine-induced enhancement of naloxone potency which is a measure of the capacity of naloxone to antagonize morphine-induced analgesia and is postulated to be an indicator of tolerance development.
    Summary · context
    The pretreatment of mice with 30 mg/kg morphine s.c. did not alter the analgesic effect of morphine in mice pretreated with saline but decreased the analgesic effect of morphine in mice pretreated with prolyl-leucyl-glycinamide (PLG).
  3. 03AnimalAnimal study (in vivo)Pharmacokinetics

    In mice, PLG did not alter whole-brain morphine levels.

    In plain wordsIn mice, PLG did not change morphine levels in the whole brain.

    Peptide
    MIF-1 (Pro-Leu-Gly-NH2)
    Outcome
    No significant changeWhole-brain morphine levels
    Study

    mousen: not reported in source

    Morphine tolerance and dependence
    Outcome group
    Pharmacokinetics · Pharmacology
    Studied dose
    Dose not stated

    Source sentences

    Summary
    PLG did not alter the whole brain levels of morphine, nor did it alter the naloxone potency in mice which were not pretreated with 30 mg/kg morphine.
  4. 04AnimalAnimal study (in vivo)Efficacy outcome

    In mice without morphine pretreatment, PLG did not alter naloxone potency.

    In plain wordsIn mice without morphine pretreatment, PLG did not change naloxone potency.

    Peptide
    MIF-1 (Pro-Leu-Gly-NH2)
    Outcome
    No significant changeNaloxone potency without morphine pretreatment
    Study

    mousen: not reported in source

    Morphine tolerance and dependence
    Outcome group
    Drug tolerance · Nervous system and cognition
    Studied dose
    Dose not stated

    Source sentences

    Summary
    PLG did not alter the whole brain levels of morphine, nor did it alter the naloxone potency in mice which were not pretreated with 30 mg/kg morphine.
  5. 05AnimalAnimal study (in vivo)Efficacy outcome

    In morphine-treated or morphine-pellet-implanted mice, PLG did not alter the naloxone amount required to induce jumping.

    In plain wordsIn morphine-treated or pellet-implanted mice, PLG did not change the naloxone amount needed to trigger jumping.

    Peptide
    MIF-1 (Pro-Leu-Gly-NH2)
    Outcome
    No significant changeNaloxone dose required for withdrawal jumping
    Study

    mousen: not reported in source

    Morphine tolerance and dependence
    Outcome group
    Drug tolerance · Nervous system and cognition
    Studied dose
    Dose not stated

    Source sentences

    Summary
    In mice treated with 100 mg/kg morphine or implanted with 50 mg morphine pellets for 24 or 72 h, the amount of naloxone required to induce jumping was not altered by PLG.
  6. 06AnimalAnimal study (in vivo)Safety outcome

    In mice, PLG treatment increased hypothermia after naloxone-induced morphine withdrawal.

    In plain wordsIn mice, PLG increased the fall in body temperature after naloxone-induced morphine withdrawal.

    Peptide
    MIF-1 (Pro-Leu-Gly-NH2)
    Outcome
    IncreaseWithdrawal hypothermia
    Study

    mousen: not reported in source

    Morphine tolerance and dependence
    Outcome group
    Adverse events · Nervous system and cognition
    Studied dose
    Dose not stated

    Source sentences

    Summary
    However, PLG treatment did increase the hypothermia and body weight loss seen after naloxone-induced withdrawal.
  7. 07AnimalAnimal study (in vivo)Safety outcome

    In mice, PLG treatment increased body weight loss after naloxone-induced morphine withdrawal.

    In plain wordsIn mice, PLG increased weight loss after naloxone-induced morphine withdrawal.

    Peptide
    MIF-1 (Pro-Leu-Gly-NH2)
    Outcome
    IncreaseWithdrawal body weight loss
    Study

    mousen: not reported in source

    Morphine tolerance and dependence
    Outcome group
    Body weight · Metabolic and weight
    Studied dose
    Dose not stated

    Source sentences

    Summary
    However, PLG treatment did increase the hypothermia and body weight loss seen after naloxone-induced withdrawal.
  8. 08AnimalAnimal study (in vivo)Safety outcome

    In morphine-dependent mice, PLG given before naloxone did not modify withdrawal hypothermia.

    In plain wordsIn morphine-dependent mice, PLG before naloxone did not change the withdrawal-related fall in body temperature.

    Peptide
    MIF-1 (Pro-Leu-Gly-NH2)
    Outcome
    No significant changeWithdrawal hypothermia after acute PLG
    Study

    mousen: not reported in source

    Morphine tolerance and dependence
    Outcome group
    Adverse events · Nervous system and cognition
    Studied dose
    Dose not stated

    Source sentences

    Summary
    Administration of PLG to morphine-dependent mice 1 h prior to naloxone did not modify the resultant hypothermia or body weight loss.
  9. 09AnimalAnimal study (in vivo)Safety outcome

    In morphine-dependent mice, PLG given before naloxone did not modify withdrawal body weight loss.

    In plain wordsIn morphine-dependent mice, PLG before naloxone did not change withdrawal-related weight loss.

    Peptide
    MIF-1 (Pro-Leu-Gly-NH2)
    Outcome
    No significant changeWithdrawal body weight loss after acute PLG
    Study

    mousen: not reported in source

    Morphine tolerance and dependence
    Outcome group
    Body weight · Metabolic and weight
    Studied dose
    Dose not stated

    Source sentences

    Summary
    Administration of PLG to morphine-dependent mice 1 h prior to naloxone did not modify the resultant hypothermia or body weight loss.

AI wrote and checked these results. AI can make mistakes, so check important results against the source.

Version history

PepBank keeps every version of the data on this study. Status changes from Retraction Watch, Europe PMC and Crossref are listed with their source.

  1. Version 2Current

    22 Oct 2026, 02:26 UTC

    Study results updated

  2. Version 1

    21 Oct 2026, 18:59 UTC

    First added · source update from Europe PMC

Subjects

Terms as the source lists them.

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