Mild environmental intervention in mother-infant interactions reduces social play behavior in rats

During early life, animals are sensitive to environmental events that may lead to short-term and long-lasting changes in their neurobiology and behavior, which could be related to increased risk for psychopathology. Neonatal handling is an experimental intervention in the mother-infant relationship. Based on previous studies, it is known to decrease rat pups' preference for maternal cues. Handling also reduces social, sexual, and fear behavior in adult animals, which is related to underlying neuroendocrine alterations. One prominent feature of adolescence is the high frequency of social behaviors such as play that appear to be necessary for proper socioemotional development. The objective of the present study was to investigate the effect of repeatedly handling pups on social play behavior during the neonatal period in juvenile Wistar rats. We found that handling consistently decreased pouncing, wrestling, and chasing play behavior on postnatal days (PND) 25, 30, and 35 compared with non-handled juveniles. As expected, sex differences were also found. Consistent with previous studies in infant and adult rats, the neonatal handling procedure also reduced affiliative behaviors in juvenile animals. The precise mechanisms by which this early intervention leads to these alterations in offspring remain to be determined, but the cumulative effects of briefly disrupting the mother-infant relationship that caused the neonatal handling may be one possible explanation.

Brief daily postpartum separations from the litter alter dam response to psychostimulants and to stress

Neonatal handling induces several behavioral and neurochemical alterations in pups, including decreased responses to stress and reduced fear in new environments. However, there are few reports in the literature concerning the behavioral effects of this neonatal intervention on the dams during the postpartum period. Therefore, the aim of the current study was to determine if brief postpartum separation from pups has a persistent impact on the dam's stress response and behavior. Litters were divided into two neonatal groups: 1) non-handled and 2) handled [10 min/day, from postnatal day (PND) 1 to 10]. Weaning occurred at PND 21 when behavioral tasks started to be applied to the dams, including sweet food ingestion (PND 21), forced swimming test (PND 28), and locomotor response to a psychostimulant (PND 28). On postpartum day 40, plasma was collected at baseline for leptin assays and after 1 h of restraint for corticosterone assay. Regarding sweet food consumption, behavior during the forced swimming test or plasma leptin levels did not differ between dams briefly separated and non-separated from their pups during the postpartum period. On the other hand, both increased locomotion in response to diethylpropion and increased corticosterone secretion in response to acute stress were detected in dams briefly separated from their pups during the first 10 postnatal days. Taken together, these findings suggest that brief, repeated separations from the pups during the neonatal period persistently impact the behavior and induce signs of dopaminergic sensitization in the dam.

Interventions in the neonatal environment in rats and their relationship to behavior in adulthood and maternal behavior

The objective of this study was to assess the role of environmental/nest components and maternal behavior after several neonatal interventions on subsequent behavioral responses. Male Wistar rats were subjected to different neonatal interventions and were later evaluated for innate fear-like behavior in adulthood. The experimental groups included nonhandled (i.e., animals were not touched), handled (i.e., animals were separated from their mother, removed from the nest, and handled for 10 min/day), brief maternal separation (i.e., the mother was removed from the homecage for 10 min/day, and the pups remained in their cages without being touched), and tactile stimulation (i.e., the mother was removed from the homecage, and pups were stimulated with a brush for 10 min/day within the nest). The mother's behavior was recorded during the neonatal period, and the male pups were later tested in the open field as adults. The results revealed that only mothers whose pups were handled had an increase in the duration of licking behavior compared with the other groups. In the open field test, we observed decreased behavioral innate fear-like responses in male adults in the handled and brief separation groups compared with the others groups. Our results confirm that interventions during the neonatal period cause stable behavioral changes (decreased innate fear) in adulthood and that absent or excessive tactile stimulation appears to be an important factor. Both repeated disruption of the mother-infant relationship and withdrawal from the environment/nest are factors that exert profound effects on the development of the animals.

Effects of Neonatal Handling and Enriched Environment Stimulation on Brain Damage in Neonatal Rats Following Hypoglycemia / 实用儿科临床杂志

Objective To explore the effects of the neonatal handling and enriched environmental stimulation on brain damage in neonatal rats with hypoglycemia.Methods Thirty-six neonatal rats were randomly divided into the normal group,hypoglycemia intervention group and the hypoglycemia non-intervention group.Those rats in hypoglycemia intervention and hypoglycemia non-intervention groups were weaned for 12 h,then the blood sugar of both groups were monitored.After neonatal rat models with hyperglycemia were prepared,the rats in hypoglycemia intervention group received the neonatal handling for 14 d and then were kept in an enriched stimulation environment for another 14 d.Rats in normal group and hypoglycemia non-intervention group were fed in the routine way.Neonatal handling was done when the rats were born for 24 h.The rat was rubbed with the brush from head to tail softly.Rats in the hypoglycemia non-intervention group was not handled.The enriched environment stimulation was used after 15 d when the rats were born.Rats in the hypoglycemia intervention group was put into the enriched environment for 1 h per day until 28 d when the rats were born,and rats in the hypoglycemia non-intervention group was put into the normal environment.Then the body weight was scaled at 0 d,7 d,14 d,21 d and 28 d when the rats were born.Space learning and memory were tested with Morris earter at their third month's age.After that,changes of pathology was observed in their occipital cortex.Results The weight increase,the ability of space learning,memory and the number of survival pyramid neurons of occipital cortex in normal group were better than those in hypoglycemia intervention and hypoglycemia non-intervention group(Pa