Superpopulação: um modelo de stress social durante o período gestacional e seus efeitos na mãe e na prole

Abstract

Stressful events have become frequent in modern society, resulting in the rise of diseases caused by stress. In this way, in this way, aim of this study is to investigate possible changes caused by stress, resulting from overpopulation, during mice’s gestation and also to evaluate their reproductive consequences, in the embryonic, fetal, placental, postpartum depression and maternal care patterns. In addition, it aims to evaluate the prenatal stress consequences in the neonates’ physical and neurological developments and also in the offspring’s behavior at puberty. In this work, Swiss mice’s females were mated with males of the same strain and the presence of the vaginal buffer was considered the 1st gestation day (gd). The pregnant females, in the stress group, were accommodated with 10 non-pregnant females throughout the gestational period, whereas the pregnant women in the control group remained in single dwellings. At 15th gd, elevated plus maze (EPM) and open field (OF) tests were performed to evaluate the behavior and some females were euthanized for morphological evaluation of the uterine horns, placentas and fetuses. In the other females, the gestation was carried out and the maternal weight gain was monitored throughout the gestation period. After birth, offspring were weighed and standardized, the physical and neurological development parameters were evaluated until the 30th postnatal day (pnd). Postpartum depression was assessed in the 2nd pnd, by the forced swimming test, maternal care (MC) observed in the 5th and 10th pnd. Offspring behavior patterns were evaluated by means of the EPM and OF tests between 30th and 32th pnd. The results indicated that overpopulation stress interferes with the pregnancy rate, decreases implantation and gestational viability, increases the number of hemorrhages and resorptions at fetal development sites, causes fetal intrauterine growth restriction (IUGR), placental weight loss and decreased efficiency of this organ. Pregnancy behavior analysis did not present significant alterations in the EPM, but they presented a less anxious behavior in relation to the females of the control group in the OF test. Overpopulation stress resulted in lower maternal weight gain at the end of gestation, reduced weight in offspring. Offspring’s physical development evaluation showed reduction in the anus-nose, nose-tail and anus-genital distances. Regarding the neurological development, there was delay in the reflexes of palmar grasping and righting. Maternal behavior’s analysis showed that females subjected to stress during the prenatal period licked their pups less in the 5th pnd. When we evaluated offspring’s behavior at puberty, female pups were less anxious than control. We can conclude that overpopulation stress significantly interferes with pregnancy index, gestational well-being, placental efficiency, neonatal size, as well as their growth in the first month of life and lead to delays in neurological development. It has also been, observed that overpopulation stress may have an anxiolytic effect on pregnancy, conferring on female offspring as a mechanism for adapting to stress.