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Social play in juvenile rats after in utero exposure to morphine
R J Niesink1, L J Vanderschuren, J M van Ree
1Dept. of Pharmacology, Rudolf Magnus Institute for Neurosciences, Faculty of Medicine, Utrecht University, The Netherlands.
Insights
Prenatal morphine exposure in rats increased social play behavior. This suggests morphine affects general reward and motivation, not the specific mechanisms of play itself.
Area of Science:
- Neuroscience
- Developmental Biology
- Behavioral Science
Background:
- Prenatal opiate exposure can alter rodent development, affecting behavior and stress responses.
- Endogenous opioid systems and receptors establish a critical balance during mammalian nervous system development.
- This balance is sensitive to prenatal opioid agonists and antagonists, influencing behavior.
Purpose of the Study:
- To investigate the impact of prenatal morphine exposure on play behavior in juvenile rats.
- To determine if morphine affects the motivational or reward aspects of play behavior.
- To analyze changes in social play using sequential behavioral analysis.
Main Methods:
- Administered morphine to pregnant rats during gestation.
- Assessed play behavior in juvenile offspring exposed prenatally to morphine or saline.
- Utilized sequential analysis to examine behavioral transitions during social play.
Main Results:
- Juvenile rats prenatally exposed to morphine exhibited elevated levels of social play.
- No significant changes were observed in non-play social behaviors or non-social activities.
- Sequential analysis revealed increased transitions between play-related behaviors, but not between non-play behaviors.
Conclusions:
- Prenatal morphine exposure enhances social play in juvenile rats.
- The findings suggest an effect on general reward or motivation systems rather than play behavior mechanisms.
- Further research is needed to elucidate the precise neurobiological pathways involved.
Abstract:
Changes in analgesia, play behavior, sexual behavior and responsiveness to stress and stimulants have been reported in rodents treated in utero with opiates. During development the endogenous opioids and opioid receptors are present in a tonic balance in the mammalian nervous system. The development of this balance is particularly sensitive to prenatal administration of opioid agonists and antagonists. The motivational and rewarding aspects of play behavior are probably controlled by endogenous opioid systems; low doses of opioids stimulate play behavior, whereas administration of opioid antagonists attenuates play behavior. We have analyzed the effect of morphine administration during the prenatal development of endogenous opioid systems on play behavior in juvenile rats. The doses of morphine used neither affected gestation of pregnant mother rats nor sensorimotor development of the juvenile rats. Levels of social play were elevated in juvenile rats after prenatal exposure to morphine. Social behaviors not related to play and non-social activities were not affected by the prenatal treatment procedure. To study these changes in more detail, social play was investigated using a sequential analysis in prenatally morphine-and saline-exposed pairs. The sequential structure of behavior was not altered by the in utero exposure to morphine. Quantitatively, increases in behavioral transitions were found between behaviors related to play. The prenatal morphine treatment did not affect transitions between behaviors not related to play. It is concluded that the prenatal exposure to morphine did not affect mechanisms underlying play behavior itself, but is probably affecting more general phenomena like reward or motivation to play.