Center for Neurobiology of Aging, PST, IRCCS INRCA, Ancona, Italy.
Section of Neuroscience and Cell Biology, Department of Experimental and Clinical Medicine, Università Politecnica delle Marche, Ancona, Italy.
Neurobiol Learn Mem. 2019 May;161:83-91. doi: 10.1016/j.nlm.2019.04.001. Epub 2019 Apr 2.
A wide agreement exists that environmental enrichment (EE) is most beneficial if introduced early in life, but numerous studies reported that also aged animals remain responsive. As age-related memory and cognition impairments are not uniform, an open question is whether EE might exert different effects in animals with different age-related deficits. A 12-week EE protocol was applied to late adult rats pretested for habituation and aversive memory. Animals were classified as low (LP) and high (HP) performers according to percent exploration change in Open Field test (OF) and as impaired (I) and not impaired (NI) according to latency in Step-through Passive Avoidance test (PA). Standard housing (SH) animals pretested by OF and PA, and naïve (non-pretested) EE and SH rats were used as controls. In comparison to pretest, after the housing protocol, EE LP ameliorated while EE HP and both SH HP and LP worsened their habituation pattern. The positive influence of EE on LP was probably due to the more active interaction with and the faster adaptation to surroundings promoted by continuous, multiple stimuli provided during the enriched housing. Regarding HP, EE did not boost the basal behavior, which likely represented the maximum achievable for that age, and the post housing exploration change dropped, as in SH animals, because of the retesting. After EE, a significant percentage of NI animals became I and a significant percentage of I animals became NI. The changes evidenced in the NI group likely depended on EE-related reduction of anxiety and the consequent more efficient coping with fearful situations. This hypothesis was strengthened by the observation that naïve EE animals were almost all I. Pretested EE I rats were not influenced by the rearing condition: their behavior was comparable to SH animals' behavior and determined by retesting. In conclusion, these results demonstrated that, when applied to aging rats, EE produces different effects based on pre-housing cognitive performances. The issue needs further analyses, but the observation that not all animals are able to take advantage of EE to the same extent suggests the opportunity to design individually tailored approaches to optimize their efficacy and minimize possible unwanted consequences.
人们普遍认为，环境丰富（EE）如果在生命早期引入，最有益，但许多研究报告称，老年动物仍然有反应。由于与年龄相关的记忆和认知障碍并不一致，因此一个悬而未决的问题是，EE 是否可能对具有不同与年龄相关缺陷的动物产生不同的影响。一项为期 12 周的 EE 方案应用于成年后期大鼠，这些大鼠在习惯化和厌恶记忆测试中进行了预测试。根据开放式场测试（OF）中探索百分比的变化，动物被分类为低（LP）和高（HP）表现者，根据步穿被动回避测试（PA）中的潜伏期，动物被分类为受损（I）和未受损（NI）。标准饲养（SH）动物通过 OF 和 PA 进行预测试，以及未经测试的 EE 和 SH 大鼠被用作对照。与预测试相比，在住房方案后，EE LP 得到了改善，而 EE HP 和 SH HP 和 LP 都恶化了它们的习惯化模式。EE 对 LP 的积极影响可能归因于在丰富的住房环境中，通过持续的、多重刺激，动物的积极互动和对环境的更快适应。对于 HP，EE 并没有增强基础行为，这可能是该年龄段所能达到的最大值，并且由于重新测试，住房后的探索变化下降，就像 SH 动物一样。EE 后，相当比例的 NI 动物变成了 I，相当比例的 I 动物变成了 NI。NI 组的变化可能取决于 EE 相关的焦虑减轻，以及随后更有效地应对恐惧情况。这一假设得到了加强，因为观察到未经测试的 EE 动物几乎都是 I。预测试的 EE I 大鼠不受饲养条件的影响：它们的行为与 SH 动物的行为相当，并且由重新测试决定。总之，这些结果表明，当应用于老年大鼠时，EE 根据住房前的认知表现产生不同的效果。这个问题需要进一步分析，但观察到并非所有动物都能够以相同的程度受益于 EE，这表明有机会设计个性化的方法来优化其效果，并最大限度地减少可能的不良后果。
