The study, conducted by Professor Tracey Shors from the department of psychology and the W. M. Keck Center for Collaborative Neuroscience at Rutgers, and graduate student Benedetta Leuner, found that female rats during the postpartum period are less anxious and more resistant to stress than females without offspring. The researchers presented their findings Monday (Nov. 10) at the annual meeting of the Society of Neuroscience in New Orleans, La.
"Our results demonstrated that postpartum female rats show very different and unique responses to stress compared to females without reproductive and maternal experience," Shors says. In virgin rats, exposure to stress severely impaired new learning and increased anxiety. In contrast, stressful events did not affect learning or anxiety behavior in rats with new offspring. The researchers theorize that some cognitive and emotional responses to stressful experiences may be suppressed during the postpartum period.
These findings are the first to show that learning is maintained in new mothers, even in the face of stressful life events. "It is probably good for new mothers to be able to learn effectively regardless of life stressors, especially when it comes to taking care of their young," says Shors. "Our results show that the female response to stressful experience is dynamic and can change dramatically during different stages of reproductive life."
Shors and Leuner believe that these data in rats may relate to mental illness in humans. Women are more susceptible than men to mental disorders associated with stress and stressful life events such as depression, generalized anxiety and posttraumatic stress disorder. By examining the impact of stress on cognitive and emotional function during various stages of reproductive life, such as the postpartum period, scientists may begin to understand the reasons for the high incidence of mental illness in females, especially postpartum depression and psychosis.
In their next studies, the researchers will be addressing the age-old question: Is it nurture or nature? Is the stress response suppressed because of behaviors that occur during motherhood, such as those directly involving nurture and care for their young, or is it mediated by the very different hormonal environment within the postpartum female?