The Effects of Maternal Deprivation and Adolescent Morphine Exposure on Anxiety-Like Behaviors and Working Memory in Male and Female Rats

Early life stress can be one of the main sources leading to individual differences in facing challenges throughout life. Maternal deprivation (MD), a model of early life stress, can cause persistent changes in brain function and may be a risk factor for later drug addiction. Adolescence is a critical period for neurodevelopmental processes. Adolescent exposure to opioids may cause changes in emotional behavior and cognitive abilities. In this study, the effects of maternal deprivation in adolescents administered morphine were investigated by examining anxiety-like behaviors and working memory in male and female rats. To induce maternal deprivation, we removed the mothers from the cages for 3 h per day from postnatal day 1 through 14. Furthermore, adolescent Wistar rats were exposed to increasing doses of morphine for 10 days on postnatal day (PND) 31–40. Behavioral tests including open field test, elevated plus maze test on PND 41 and working memory evaluation with y-maze test on PND 42 were performed on these animals. Morphine exposure during adolescence led to decreased anxiety and working memory impairment in male and female adolescent animals but had no effect on motor activity. Maternal deprivation and morphine exposure had no effect on motor activity, or anxiety-like behavior but resulted in working memory impairment. Chronic morphine administration can lead to cognitive changes and decreased anxiety in both male and female animals. Meanwhile, maternal deprivation stress does not seem to affect these behaviors significantly, but it does interact with morphine administration to impair working memory. These results highlight the importance of considering environmental factors in understanding the effects of adolescence on brain development and behaviors.