Impacto da limitação na construção do ninho sobre o aprendizado e memória da prole pré-púbere

Abstract

Maternal behaviors observed during the postnatal period play a crucial role in the neurocognitive development of offspring. The Nest Building Limitation (NBL) model

emerges as an essential tool to simulate natural stressors, affecting the mother- offspring relationship. The conscious restriction of access to nesting materials exposes

offspring to stress early on, being instrumental in analyzing the implications of these experiences on information processing and the formation of lasting memories. Thus, the main objective of this study was to investigate the impacts on offspring cognition during the early stages of life, resulting from the NBL stress model in the postnatal and lactation period. The experiments were conducted using pregnant Wistar rats, divided into control and NBL groups. On Postnatal Day 1 (PND1), the litters were standardized to 4 males and 4 females and weighed at 3-day intervals, while the mothers were weighed at the same intervals. From PND2 to PND9, the animals in the NBL group were subjected to the NBL model, and the control with abundant wood shavings. Maternal behaviors (MB) were assessed from PND4 to PND9, and behavioral tests were conducted on the offspring from PND27 to PND33, including the Morris Water Maze (MWM) for spatial memory assessment, Object Recognition (OR) for object recognition memory, Contextual Fear Conditioning (CFC) to assess aversive memory, and the Open Field Test (OFT) for evaluating locomotion and immobility time. The OFT

in the mothers was performed on PND6. For statistical analysis, Student's t-test or two- way ANOVA with repeated measures followed by Tukey's post-test was used. The

results revealed a lower litter weight in the LCN group during the lactation period compared to the control group animals. Regarding MB, there was a decrease in maternal parameters and an increase in non-maternal ones in the LCN group animals compared to the control group animals. In the MWM test, during the training days, the LCN group animals (females and males) took longer to reach the platform, and on the test day, the LCN group animals spent less time in the platform quadrant compared to the control group. In the OR test, a decrease in exploration time of the new object was observed in the LCN group animals in the 2 and 24-hour tests, respectively, compared to the control group animals, consequently, the LCN group animals showed a lower recognition index in the 2 and 24-hour tests relative to the control group animals. In the OFT, no differences were observed in the parameters evaluated, both in the mothers and in the offspring. In the CFC test, a shorter freezing time was observed in the LCN group animals compared to the control group animals. It can be concluded that the induction of perinatal stress by LCN was capable of reducing maternal behavior parameters, resulting in implications for the offspring. The LCN group animals demonstrated deficits in memory, both in terms of spatial memory and object recognition. Furthermore, a deficit in aversive memory was evidenced, indicating difficulty in remembering or reacting to the context associated with the aversive stimulus, thus demonstrating that LCN had a significant impact on memory and learning in prepubertal rats.