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Participação do sistema opioidérgico e dos glicocorticóides nas alterações comportamentais e da imunidade inata induzidas na prole pelo estresse pré-natalDue to its rapid growth, the fetus is particularly vulnerable to insults and the attendant changes in its hormonal milieu. This led to the suggestion that adverse life situations experienced by the pregnant mother can induce alterations in the fetal environment and result in deleterious effects on the rate of development and health of the child. In view of the considerable methodological difficulties in assessing the impact of the stress on human mothers, and evaluating its effects on the development and behavior of their children, much of our information about sequelae from gestational stress has been derived from studies in experimental animals. That was the objective of this study, taking into account the required grounds for reasonable comparisons. We particularly aimed the effects of prenatal stress applied from gestational day (GD) 15 to GD19 on behavior, immunological parameters, levels of corticosterone and testosterone and brain neurochemistry of male and female Swiss mice offspring, on post natal day 30. We also study the effects of naloxone (opioid antagonist) and of metyrapone (corticosterone synthesis inhibitor), both applied before prenatal stress, on parameters described above. The results of this work showed that: 1) prenatal stress increased total locomotion in males evaluated in an open field and naloxone treatment before stress prevented this effect; 2) prenatal stress and metyrapone injection increased anxiety levels of male and female offspring. Metyrapone injection before prenatal stress prevented this effect; 3) naloxone, alone or associated to prenatal stress, decreased oxidative burst of blood neutrophils in male and female pups. On the other hand, in female offspring naloxone alone increased blood neutrophil phagocytosis; 4) prenatal stress decreased phagocytosis of peritoneal macrophage and naloxone before stress prevented this effect; 5) prenatal stress decreased oxidative burst and phagocytosis of peritoneal macrophage in female pups and naloxone treatment before stress prevented this effect; 6) prenatal stress decreased corticosterone serum levels in male offspring and naloxone treatment, alone or associated to stress increased it. 7) In female pups, prenatal stress increased corticosterone serum levels and metyrapone before stress prevented this alteration; 8) gestational stress increased Nor turnover in male and female offspring; 9) naloxone increased DA turnover only in male offspring; 10) metyrapone treatment increased DA turnover in male and female offspring; 11) prenatal stress, naloxone or metyrapone treatment had different effects on male and female offspring. Altogether, these findings show that prenatal stress has relevant effects on animal development; these effects last until adulthood. The results also show that many of prenatal stress effects can be prevented by naloxone or metyrapone, and suggests that the opioid sys...