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Enhanced sensitivity to naltrexone-induced drinking suppression of fluid intake and sucrose consumption in maternally separated rats

Pharmacology Biochemistry and Behavior
Publication Date
DOI: 10.1016/j.pbb.2007.03.007
  • Maternal Separation
  • Stress
  • Sex Difference
  • Postnatal
  • Sucrose
  • Naltrexone
  • Reward
  • Opioid


Abstract Early-life stress has been identified as a risk factor in the development of a host of disorders, including substance abuse; however the link between early postnatal stress and changes in measures of reward has not been thoroughly researched. The current study had two main objectives: 1) to determine the impact of maternal separation (an animal model of early-life stress) on the consumption of 10% and 2.5% sucrose solutions by Long–Evans rat dams and male and female offspring, and 2) to determine the effect of the opioid antagonist naltrexone (0.1–3.0 mg/kg) on drinking by each of those groups. Dam-pup separations occurred for varying lengths of time during the first two postnatal weeks. In Experiment 1, a two-bottle choice test (sucrose solution vs. water) was administered across five days to both nonhandled (NH) and maternally-separated (MS) offspring as adults and to dams 2–4 weeks post-weaning. In Experiment 2, naltrexone was administered prior to two-bottle choice tests. MS males and the dams of MS litters exhibited increased intake of total fluid and sucrose solutions, whereas results from females were less consistent. Naltrexone elicited a greater decrease in fluid intake and sucrose intake in male MS offspring compared to male NH offspring. These results indicate that early postnatal stress alters both sucrose consumption, a non-drug measure of reward, and apparently the brain opioid systems that mediate naltrexone-induced drinking suppression.

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