Effects of a new postnatal stress model on monoaminergic neurotransmitters in rat brains

Abstract

Introduction: Stress and environmental perturbations influence postnatal brain development and may account for the high disability rates of preterm survivors following intensive care treatment. This study aims to investigate the impact of early environmental factors on the monoaminergic neurotransmitter system in the developing rat brain by using an innovative neonatal stress model. Materials and methods: After birth, in the experimental groups newborn rats were separated from their mothers and exposed to different stressful stimuli four times a day on day P0 to P6 for 10min each. To mimic intensive care treatment, the stress protocol applied environmental factors like bright light, noise, and low temperature alternating with pain and handling stress at day- and night-time in a varying sequence. The non-stressed control mothers and litters were left completely undisturbed until sacrificing on day P7 or P20. Results: Brains of stressed animals revealed significantly higher levels of norepinephrine (NE) and dopamine (DA) as determined by HPLC-ED and electrochemical detection at day P7 as compared to controls. When returned to their mothers’ undisturbed care, juvenile rats at day P20 still showed higher (yet statistically not significant) concentrations of NE and DA in brain. The stressed animals gained less weight with significantly lower body weights at day P7 compared to controls. Their mothers developed various forms of stressed behaviour. Conclusions: A novel animal model for postnatal intensive care stress was established leading to changes in brain monoamine levels of newborn rats, while undisturbed maternal care seems to moderate the stress effects subsequently.