Prenatal morphine enhances morphine-conditioned place preference in adult rats

Pharmacol Biochem Behav. 1997 Oct;58(2):525-8. doi: 10.1016/s0091-3057(97)00281-5.


Conditioned place preference (CPP) is a commonly used method for assessing the rewarding qualities of drugs, including opiates. In the present study, we examined long-term effects of prenatal morphine on morphine-associated place preference. Pregnant Fischer 344 rats were given increasing doses of morphine (0.75-12.0 mg/day) in slow-release emulsion during gestational days 12-18. Control rats were injected with vehicle and were fed either with morphine rats or ad libitum. At birth, all litters were culled to 8 pups and fostered to naive dams. Testing began when rats were 10-12 weeks old. Rats prenatally exposed to morphine exhibited a significantly higher preference for the morphine-paired compartment, suggesting that prenatal morphine induces a long-lasting enhancement of its reinforcing effect. Thus, prenatal morphine may result in enhanced activity and/or sensitivity of the endogenous opiate system, thereby placing the organism at higher risk for opiate drug abuse.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Conditioning, Psychological / drug effects*
  • Female
  • Maternal Exposure*
  • Morphine / pharmacology*
  • Narcotics / pharmacology*
  • Opioid-Related Disorders
  • Pregnancy
  • Rats
  • Rats, Inbred F344
  • Reward
  • Task Performance and Analysis


  • Narcotics
  • Morphine