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Related Experiment Videos

Enkephalin levels decrease in rat striatum during morphine abstinence.

L Bergström, L Terenius

    European Journal of Pharmacology
    |December 20, 1979
    PubMed
    Summary
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    Repeated morphine exposure in rats significantly reduced striatal enkephalin levels 24 and 48 hours after withdrawal. A single morphine dose did not alter these opioid peptide levels.

    Area of Science:

    • Neuroscience
    • Pharmacology
    • Biochemistry

    Background:

    • Opioid peptides, such as enkephalins, play crucial roles in pain modulation and reward pathways.
    • Morphine is a potent opioid analgesic that interacts with these systems.
    • Understanding the long-term effects of chronic morphine use on endogenous opioid systems is vital for managing addiction and withdrawal.

    Purpose of the Study:

    • To investigate the impact of chronic morphine administration on striatal enkephalin levels in male Sprague-Dawley rats.
    • To determine the time course of changes in enkephalin levels following morphine withdrawal.
    • To assess the effect of a single high dose of morphine on enkephalin levels.

    Main Methods:

    • Male Sprague-Dawley rats were administered morphine daily for 11 days.

    Related Experiment Videos

  • Control rats received saline injections.
  • Striatal enkephalin levels were quantified using radioimmunoassay at 2, 24, and 48 hours post-withdrawal.
  • Enkephalin levels were also measured 12 and 24 hours after a single 20 mg/kg morphine dose.

    • Main Results:

    • Chronic morphine treatment led to no significant change in striatal enkephalin levels at 2 hours after the last injection.
    • A marked reduction in enkephalin levels was observed 24 hours after withdrawal.
    • A slight decrease in enkephalin levels persisted at 48 hours post-withdrawal.
    • A single dose of morphine (20 mg/kg) did not alter enkephalin levels at 12 or 24 hours.

    Conclusions:

    • Chronic morphine exposure induces a delayed and sustained reduction in striatal enkephalin levels.
    • These findings suggest that prolonged opioid use disrupts the endogenous enkephalinergic system.
    • The observed changes may contribute to the neurobiological adaptations underlying opioid dependence and withdrawal symptoms.