Influência da redução de ninhada sobre o comportamento materno e respostas comportamentais e endócrinas da prole na fase adulta

Abstract

In rats the mother is essential for the survival of offspring, especially during the first two weeks of life. The maternal care (CM) spent by females has great importance for the proper development of the offspring. Thus, changes during the perinatal period are able to trigger disturbances in the relationship and can lead to lasting behavioral and neuroendocrine changes in the offspring. Likewise, nutritional and hormonal states in early stages of development (pregnancy and lactation) are related to epigenetic changes that may lead to the development of diseases. In experimental studies, neonatal overfeeding by reducing the number of pups per litter of offspring causes obesity and increases the risk of cardiovascular disease. In the present study we evaluated the influence of the reduction of litter on maternal care in lactating rats and possible consequences of endocrine and behavioral responses in the offspring during adulthood. To induce overeating neonatal, on the 2nd day of lactation (DL), the litter size was reduced to three pups (2 males and 1 female, NR group) and control group (NN) was set to 12 pups (maximum 6 males per litter). The CM was investigated during the lactation through assessment of maternal behavior, maternal anxiolysis and aggressive behavior. The effect of reducing litter in the adult offspring (60 days) on food intake, body weight, body composition, biochemical and hormonal levels were analyzed, in addition to behavioral responses. Differences were considered significant when p < 0.05. The results showed that there was a significant increase in total maternal behavior mainly in the behavior of licking pups and arched-nursing, and a decrease in the total maternal behavior (diet and time away from the pups) in mothers caring reduced litter. These rats also showed reduced anxiety-related behavior and increased aggressive behavior, especially in the first 2 weeks. Concerning to offspring, the NR group showed increased weight from the 8th DL to adulthood, both males and in females. These animals still showed up hyperphagic weaning until adulthood and increase adipose tissue: epididymal fat, ovarian fat and retroperitoneal fat (in males and female). The biochemical profile of NR animals was representative of dyslipidemia, with increases in serum glucose, triglycerides, total cholesterol, VLDL-c, LDL-c and decrease in HDL-c. Neonatal overfeeding caused hyperleptinemia in both sexes and increased insulin in females, which is apparently associated with the framework of insulin resistance and glucose intolerance displayed by these animals. Regarding behavioral responses, animals raised in small litter showed behaviors related to anxiety and fear reduced, as their mothers. Thus, it is concluded that ''maternal environment" favored by the reduction in litter size was crucial to the development of metabolic and behavioral changes in the adult offspring