Neonatal interventions differently affect maternal care quality and have sexually dimorphic developmental effects on corticosterone secretion.

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 10days 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.

Maternal depression model: long-lasting effects on the mother following separation from pups.

This study was carried out to ascertain the effects of maternal separation (3 h per day) of mothers from their pups in the neonatal period in rats, which has been suggested to induce a depressive-like state, would have long lasting effects on different parameters including hippocampal Na(+), K(+)-ATPase activity, NO production, free radical production and antioxidant enzymes activities in dams. Fourty-eight Wistar rats were divided into 3 groups: control, brief separation (10 min) and long separation (3 h). The neonatal interventions were done on postpartum days 1-10. At 35 days post-partum the dams were killed and the hippocampal Na(+), K(+)-ATPase activity were measured, as well as the activity of the antioxidant enzymes catalase, glutathione peroxidase, superoxide dismutase, free radicals production, and the production of nitric oxide. Hippocampal Na(+), K(+)-ATPase activity was decreased in the brief separated group and in dams subjected to 3 h separation from their pups. A reduction in nitric oxide levels in the hippocampus in dams of the long separated group was also observed. It is concluded that the withdrawal of pups from their mothers make the mothers more susceptible to the development of neurochemical alterations that could be related to depressive features.