Eduardo Toigo

Neonatal handling (H) and maternal separation (MS) both induce changes in maternal care, but the contribution of these changes to the behavioral and neurochemical outcomes of the offspring remains unclear, as studies often find opposite results concerning the frequency of maternal behaviors, particularly in the MS paradigm. In this study, behavior displayed by H, MS and non-handled (NH) Wistar rat dams were observed during the first 10 days after birth. A tentative assessment of the quality of maternal care was made, using a previously reported score that reflects behavior fragmentation and inconsistency. Central oxytocin levels and hippocampal synaptic plasticity markers were also evaluated in dams, immediately after litter weaning. In adulthood, male and female offspring were subjected to a contextual stress-induced corticosterone challenge to provide further information on the impact of early interventions on neuroendocrine parameters. We found that while both H and MS interventions induced an increase in the amount of pup-directed behavior, MS dams displayed a more fragmented and inconsistent pattern of care, reflecting poorer maternal care quality. Interestingly, an increase in oxytocin levels was observed only in H dams. While H offspring did not differ from NH, MS males and females showed marked differences in corticosterone secretion compared to controls. Our results suggest that briefly removing the pups from the nest alters maternal care quantity but not quality and increases central oxytocin, while long separations appear to increase low quality maternal care and change neuroendocrine responses in adult offspring in a sex-specific manner.

Caffeine is widely consumed in beverages and food, and its consumption in high doses is associated with anxiety increase. Stress situations are often associated to coffee consumption, and have a strong influence on oxidative DNA damage. As there are sex-specific differences in many metabolic, neurochemical and behavioral aspects, the aim of this study is to verify the interaction between chronic consumption of caffeine and chronic stress on anxiety and DNA breaks in the hippocampus on male and female rats. Wistar rats were submitted to restraint stress for at least 50 days. The diet consisted of standard rat chow and caffeine 0.3 or 1 g/L in drinking water "ad libitum" as the only drinking source. Controls received tap water. Anxiety-like behavior and DNA breaks in the hippocampus were evaluated. Caffeine consumption and chronic stress increased anxiety-like behavior as well as DNA breaks in the hippocampus of male rats. No effect on these parameters was observed in females. These results may be related to the presence of estradiol, which may have anxiolytic and neuroprotective properties.

We studied the effect of chronic caffeine on parameters related to oxidative stress in different brain regions of stressed and non-stressed rats. Wistar rats were divided into three groups: control (receiving water), caffeine 0.3 g/L and caffeine 1.0 g/L (in the drinking water). These groups were subdivided into non-stressed and stressed (repeated restraint stress during 40 days). Lipid peroxide levels and the total radical-trapping potential were assessed, as well as antioxidant enzyme activities superoxide dismutase, gluthatione peroxidase, and catalase in hippocampus, striatum and cerebral cortex. Results showed interactions between stress and caffeine, especially in the cerebral cortex, since caffeine increased the activity of some antioxidant enzymes, but not in stressed animals. We concluded that chronic administration of caffeine led, in some cases, to increased activity of antioxidant enzymes. However, these effects were not observed in the stressed animals.