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Morphine withdrawal-facilitated aggression is attenuated by morphine-conditioned stimuli
1Laboratory of Behavioural Pharmacology, Department of Psychopharmacology, Valdman Institute of Pharmacology, Pavlov Medical University, 6/8 Lev Tolstoy Street, St. Petersburg 197089, Russia. behav@spmu.rssi.ru
Abstract:
There is a considerable body of evidence indicating that stimuli associated with drug administration may become conditioned and evoke drug-like effects. The purpose of this study was to evaluate the ability of morphine-paired stimuli to affect an expression of morphine withdrawal-facilitated aggression. Individually housed aggressive adult mice were subjected to the repeated subcutaneous administration of morphine (twice a day, 8 days, increasing doses 10-80 mg/kg). Morphine treatment cessation facilitated an aggressive behaviour of animals during the second day of withdrawal. Subcutaneous but not intraperitoneal injection of saline attenuated the aggressive behaviour in morphine-withdrawn mice. These results suggest that the site of drug injection may serve as a conditioned stimulus.
Insights
Drug-associated cues can trigger drug-like effects. This study found that the injection site for morphine acted as a conditioned stimulus, reducing withdrawal-induced aggression in mice.
Area of Science:
- Neuroscience
- Behavioral Pharmacology
- Addiction Research
Background:
- Conditioned stimuli associated with drug administration can elicit drug-like effects.
- Understanding these conditioned responses is crucial for addiction research.
Purpose of the Study:
- To investigate if morphine-associated stimuli can influence morphine withdrawal-facilitated aggression.
- To determine the role of the injection site as a conditioned stimulus.
Main Methods:
- Adult mice received repeated subcutaneous morphine injections over 8 days.
- Aggressive behavior was assessed during morphine withdrawal.
- Saline injections (subcutaneous and intraperitoneal) were administered to withdrawn mice.
Main Results:
- Morphine withdrawal significantly increased aggressive behavior in mice.
- Subcutaneous saline injections attenuated this withdrawal-induced aggression.
- Intraperitoneal saline injections did not affect aggression.
Conclusions:
- The site of drug (morphine) administration can function as a conditioned stimulus.
- This conditioned stimulus can modulate the expression of withdrawal-related behaviors, such as aggression.