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Aggression during morphine withdrawal: effects of method of withdrawal, fighting experience, and social role
Abstract:
Offensive and defensive components of aggressive behavior were determined in resident and intruder mice. Withdrawal aggression was measured after the removal of a subcutaneous morphine pellet or after precipitation by naloxone in naive mice and after removal of a morphine pellet in mice with prior fighting experience. In naive mice, removal of a morphine pellet led to increases in attack bites and threats but naloxone-precipitated withdrawal led to decreases in these behaviors and to increases in defensive posturing, escape attempts and vocalizations. Prior fighting experience abolished the enhanced attack behaviors of resident mice following morphine pellet removal, but led to heightened defensive behavior in intruder mice. The behavior of intruder mice appeared more sensitive to naloxone administration than the behavior of resident mice; naloxone influenced not only intruder defensive behavior, but also other non-aggressive behaviors. The social role of the drug recipient and his prior history of aggressive behavior are important determinants of morphine and naloxone effects on aggression.
Insights
Morphine withdrawal and naloxone can alter aggression in mice. Prior fighting experience significantly impacts how mice respond to these substances, influencing both offensive and defensive behaviors.
Area of Science:
- Neuroscience
- Behavioral Pharmacology
- Animal Models
Background:
- Aggressive behavior is complex, involving both offensive and defensive components.
- Opioid withdrawal, induced by morphine, can precipitate distinct behavioral changes.
- Naloxone, an opioid antagonist, is used to precipitate withdrawal symptoms.
Purpose of the Study:
- To investigate the effects of morphine withdrawal and naloxone administration on offensive and defensive aggression in resident and intruder mice.
- To determine the influence of prior fighting experience on these drug-induced behavioral changes.
Main Methods:
- Resident-intruder paradigm was used in mice.
- Morphine pellet implantation was employed to establish dependence.
- Naloxone was administered to precipitate withdrawal.
- Behavioral components of aggression (attack bites, threats, defensive posturing, escape) were quantified.
Main Results:
- In naive mice, morphine pellet removal increased attack behaviors, while naloxone precipitated withdrawal decreased attack behaviors and increased defensive behaviors.
- Prior fighting experience in resident mice abolished enhanced attack behaviors post-morphine withdrawal.
- Prior fighting experience in intruder mice heightened defensive behaviors.
- Intruder mice showed greater sensitivity to naloxone than resident mice, affecting non-aggressive behaviors too.
Conclusions:
- The effects of morphine and naloxone on aggression are modulated by the social role (resident vs. intruder) and prior aggressive history of the animal.
- Opioid withdrawal and antagonism have differential impacts on offensive and defensive aggression, influenced by context and experience.