Experiences during early development can profoundly alter the structure, function, and regulation of neuroendocrine systems. In this study we used the maternal separation (MS) as a source of early stress. Male and female rat pups were separated daily from their mothers for 5 hours between 09:00 and 14:00 on postpartum days (PD) 2 to 7 and 10 to 15 PD. Control litters remained undisturbed in the maternal cage. In adolescent we examined the effects of neonatal MS on measures of orienting, impulsive, general activity and anxiety behaviour. Indeed we evaluated the effects of infant mother separation on monoaminergic systems development. Dopamine (DA) and serotonin (5-HT) contents were determined in the areas of the brain directly related to such behaviours in adolescent rats. The prolonged MS during the first weeks of life resulted in decreased orienting and impulsive and increased activity behaviour in adolescence. The results from the plus-maze test shown differences in the anxious response between the treated and control group with sexual differences. An alteration in brain monoamine levels were observed too suggesting that early stress induced by maternal separation on childhood can also affect monoaminergic brain system development.

Acknowledgments: This work was supported by Grant PR 41/06-15057