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Mu- and kappa-opioid receptor-mediated opioid effects on social play in juvenile rats
L J Vanderschuren1, R J Niesink, B M Spruijt
1Department of Medical Pharmacology, Rudolf Magnus Institute for Neurosciences, Faculty of Medicine, Utrecht University, The Netherlands.
Abstract:
Previously, morphine has been shown to influence social play behavior in rats on two levels. An increasing effect on social play was interpreted as an effect on the rewarding aspects of social play. A lower dose of morphine abolished the effects of an unfamiliar environment on social play, supposedly by affecting the integration of environmental stimuli. In the present study the effects of receptor-specific opioid drugs on social play and measures of social behavior unrelated to play were investigated. Fentanyl, a mu-opioid receptor agonist, seemingly mimicked both effects of morphine. The mu-opioid receptor antagonist, beta-funaltrexamine, decreased social play, although a low dose of this drug increased it. BUBUC (Tyr-D-Cys(StBu)-Gly-Phe-Leu-Thr(OtBu)) and naltrindole, a delta-opioid receptor agonist and delta-opioid receptor antagonist, respectively, had no effects on social behavior. The kappa-opioid receptor agonist, U50,488H (trans-3,4-dichloro-N-methyl-N-[2-(1-pyrrolidinyl)-cyclohexyl]- benzeneacetamide), dose dependently suppressed all measures of social behavior. The kappa-opioid receptor antagonist, nor-binaltorphimine, abolished the effect of an unfamiliar environment on social play. These studies suggest that the opioidergic effect on social play is mediated through mu- and kappa-opioid receptor systems.
Insights
Opioid drugs significantly impact social play in rats. Mu-opioid and kappa-opioid receptor systems are key mediators of these effects on social behavior and environmental responses.
Area of Science:
- Neuroscience
- Behavioral Pharmacology
- Opioid Receptor Research
Background:
- Morphine influences rat social play by affecting reward and environmental stimulus integration.
- Previous research indicates a dual role for morphine in modulating social interactions.
Purpose of the Study:
- To investigate the effects of receptor-specific opioid drugs on social play and other social behaviors in rats.
- To elucidate the specific opioid receptor systems involved in mediating these behavioral effects.
Main Methods:
- Administration of various opioid receptor agonists and antagonists (fentanyl, beta-funaltrexamine, BUBUC, naltrindole, U50,488H, nor-binaltorphimine).
- Observation and measurement of social play behavior and other social behaviors in rats.
- Assessment of the impact of unfamiliar environments on social play.
Main Results:
- Fentanyl (mu-opioid agonist) mimicked morphine's effects.
- Kappa-opioid receptor agonist U50,488H suppressed social behavior; its antagonist nor-binaltorphimine blocked environmental effects on play.
- Mu-opioid receptor antagonist beta-funaltrexamine decreased play, while delta-opioid drugs had no effect.
Conclusions:
- Opioidergic modulation of social play is primarily mediated by mu- and kappa-opioid receptor systems.
- Specific opioid receptors play distinct roles in the rewarding and environmental aspects of social behavior.