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Time-dependent effects of oral morphine on autotomy following brachial nerve section in the rat
1Department of Anesthesiology, School of Medicine, Chiba University, Japan.
Abstract:
In this study, the effects of morphine in drinking water on autotomy in male F344 rats having undergone brachial nerve sections were assessed during a 3-week period. Morphine was self-administered orally in tap water by the rats. Rats administered morphine just after the nerve section or 1 week after the nerve section showed a significant increase in the severity of autotomy when compared to the rats administered distilled water. Morphine had no effect on autotomy when it was administered 2 weeks after the nerve section. These results suggested that the effect of oral morphine on autotomy changes in a time-dependent manner.
Insights
Oral morphine intake increased autotomy severity in rats after brachial nerve injury. The pain-related behavior was time-dependent, with effects observed when morphine was given soon after injury but not later.
Area of Science:
- Neuroscience
- Pharmacology
- Animal models of disease
Background:
- Autotomy, a self-mutilating behavior, is a common sign of neuropathic pain in animal models.
- Opioid analgesics like morphine are frequently used to manage pain, but their effects on neuropathic pain behaviors can be complex.
Purpose of the Study:
- To investigate the impact of orally administered morphine on autotomy in male F344 rats following brachial nerve section.
- To determine if the timing of morphine administration influences its effect on autotomy severity.
Main Methods:
- Male F344 rats underwent brachial nerve section.
- Morphine was self-administered orally via drinking water.
- Autotomy was assessed over a 3-week period, with morphine administered at different time points post-nerve section (immediately, 1 week, or 2 weeks).
Main Results:
- Rats receiving morphine immediately or 1 week after nerve section exhibited significantly increased autotomy severity compared to controls receiving distilled water.
- Morphine administration 2 weeks post-nerve section did not significantly alter autotomy severity.
- These findings indicate a time-dependent effect of oral morphine on autotomy.
Conclusions:
- The efficacy of oral morphine in modulating autotomy behavior following nerve injury is dependent on the timing of administration.
- Early intervention with oral morphine may exacerbate neuropathic pain behaviors, while later administration may have no significant effect.