Environmental enrichment reduces brain excitability in adult rats overnourished during lactation

ABSTRACT Objective: This study aimed to analyze whether exposure to environmental enrichment (EE) during the juvenile phase of life interferes with the electrical activity of the adult rat brain. In addition, the present research also investigated whether this putative effect on brain electrical activity could be affected by prior overnutrition during lactation. Electrophysiology was measured through cortical spreading depression (CSD), a phenomenon related to brain excitability. Methods: Wistar rats were suckled in litters of either nine or three pups, forming the nourished (N) or overnourished (ON) groups, respectively. At 36 days old, half of the animals from each nutritional condition were exposed to EE. The other half was kept in the standard environment (SE). At 90-120 days of life, each animal was anesthetized for CSD recordings. Results: Overnutrition during lactation caused increases (p < 0.05) in body and brain weights. The EE decelerated CSD propagation velocity regardless of nutritional state during lactation (p < 0.001). The CSD deceleration in the N-EE group was 23.8% and in the ON-EE group was 15% in comparison with the N-SE and ON-SE groups, respectively. Conclusion: Our data demonstrated that EE exposure in the juvenile phase of the rat's life reduced brain excitability, and this effect was observed even if animals were overnourished during lactation. An EE could be considered an adjuvant therapeutic resource to modulate brain excitability.

摘要
研究目的：本研究旨在分析幼年阶段暴露于环境丰富化（environmental enrichment, EE）是否会影响成年大鼠的大脑电活动。此外，本研究还探讨了泌乳期营养过剩是否会对这种大脑电活动的潜在效应产生影响。研究通过皮层扩布性抑制（cortical spreading depression, CSD）——一种与大脑兴奋性相关的现象——来测量电生理学指标。

研究方法：将Wistar大鼠按每窝9只或3只幼崽进行泌乳饲养，分别构建营养正常组（N）与营养过剩组（ON）。在大鼠36日龄时，将每个营养组中的一半个体暴露于环境丰富化环境，其余个体则饲养于标准环境（standard environment, SE）中。当大鼠生长至90~120日龄时，对每只动物进行麻醉以开展皮层扩布性抑制记录。

研究结果：泌乳期营养过剩会导致大鼠体重与脑重增加（p < 0.05）。无论泌乳期的营养状态如何，环境丰富化均会减缓皮层扩布性抑制的传播速度（p < 0.001）。与各自对应的N-SE组与ON-SE组相比，N-EE组的皮层扩布性抑制传播速度减缓了23.8%，ON-EE组则减缓了15%。

研究结论：本研究数据表明，在大鼠幼年阶段暴露于环境丰富化可降低大脑兴奋性，且即使大鼠在泌乳期存在营养过剩的情况，该效应依然存在。环境丰富化可被视为调节大脑兴奋性的辅助治疗手段。