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Updated: Aug 15, 2026

Assessment of Morphine-induced Hyperalgesia and Analgesic Tolerance in Mice Using Thermal and Mechanical Nociceptive Modalities
07:23

Assessment of Morphine-induced Hyperalgesia and Analgesic Tolerance in Mice Using Thermal and Mechanical Nociceptive Modalities

Published on: July 29, 2014

The effects of cholinergic agents on morphine-induced circling behavior in the intact mouse

E R Seidel, J M Beaton, R S Teague

    European Journal of Pharmacology
    |June 1, 1979
    PubMed

    Insights

    Morphine causes dose-dependent circling behavior in mice. This effect is amplified by muscarinic receptor blockade and reduced by muscarinic agonists, indicating a role for cholinergic systems in morphine-induced motor activity.

    Area of Science:

    • Neuropharmacology
    • Behavioral Neuroscience

    Background:

    • Morphine is a potent opioid analgesic with complex effects on motor activity.
    • Stereotyped behaviors, such as circling, can be induced by various neuroactive substances.

    Purpose of the Study:

    • To investigate the effects of morphine on locomotor activity in mice.
    • To explore the role of the cholinergic system in morphine-induced circling behavior.

    Main Methods:

    • Administration of morphine to mice to observe locomotor activity.
    • Assessment of circling behavior in response to varying morphine doses.
    • Evaluation of the modulatory effects of muscarinic receptor antagonists (atropine) and agonists (oxotremorine) on morphine-induced circling.
    • Testing the impact of a mixed muscarinic/nicotinic agonist (physostigmine).

    Main Results:

    • Morphine induced a dose-dependent, stereotyped circling behavior in mice.
    • High doses of morphine resulted in near-exclusive circling.
    • Atropine potentiated morphine-induced circling.
    • Oxotremorine attenuated morphine-induced circling.
    • Physostigmine did not significantly affect morphine-induced circling.

    Conclusions:

    • Morphine significantly alters locomotor activity in mice, primarily through inducing circling.
    • The muscarinic cholinergic system plays a crucial role in modulating morphine-induced circling behavior.
    • Muscarinic receptor blockade enhances this behavior, while agonism reduces it.

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