Maternal factors and monoamine changes in stress-resilient and susceptible mice: Cross-fostering effects

Genetic factors influence stressor-provoked monoamine changes associated with anxiety and depression, but such effects might be moderated by early life experiences. To assess the contribution of maternal influences in determining adult brain monoamine responses to a stressor, strains of mice that were either stressor-reactive or -resilient (BALB/cByJ and C57BL/6ByJ, respectively) were assessed as a function of whether they were raising their biological offspring or those of the other strain. As adults, offspring were assessed with respect to stressor-provoked plasma corticosterone elevations and monoamine variations within discrete stressor-sensitive brain regions. BALB/cByJ mice demonstrated poorer maternal behaviors than C57BL/6ByJ dams, irrespective of the pups being raised. In response to a noise stressor, BALB/cByJ mice exhibited higher plasma corticosterone levels and elevated monoamine turnover in several limbic and hypothalamic sites. The stressor-provoked corticosterone increase in BALB/cByJ mice was diminished among males (but not females) raised by a C57BL/6ByJ dam. Moreover, increased prefrontal cortical dopamine utilization was attenuated among BALB/cByJ mice raised by a C57BL/6ByJ dam. These effects were asymmetrical as a C57BL/6ByJ mice raised by a BALB/cByJ dam did not exhibit increased stressor reactivity. It appears that stressors influence multiple neurochemical systems that have been implicated in anxiety and affective disorders. Although monoamine variations were largely determined by genetic factors, maternal influences contributed to stressor-elicited neurochemical changes in some regions, particularly dopamine activation within the prefrontal cortex.