The present study aimed to establish the effect of time of the day on habituation in the open-field test, one of the most elementary forms of non-associative hippocampal-dependent learning. Open-field test was performed in young adult male Wistar rats at the beginning (08:30-10:00 h; defined as Zeitgeber time (ZT) ZT0.5-2), mid-time (13:00-14:30 h, ZT5-6.5) and at the end (18:30-20:00 h, ZT10.5-12) of the light period. Our results revealed that in the acquisition trial there were no significant differences among the six parameters recorded through tested periods. In contrast, the level of habituation in the ambulation and rearing rose as followed: ZT0.5-2 < ZT10.5-12 < ZT5-6.5. In both trials, the principal component analysis highlights two components: component 1 was mainly loaded by ambulation in the outer and inner area, rearing and freezing behaviors, whereas component 2 was mostly loaded on grooming activity and defecation. The correlation between parameters varied across the period of day and trial. Animals that expressed a higher level of grooming, defecation (ZT5-6.5) and freezing behavior (ZT0.5-2 and ZT5-6.5) at acquisition trial habituated better on those parameters on the retention trial. In conclusion, habituation outcomes to the open-field test and correlation between tested parameters highly depend on daytime.

中文翻译：

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大鼠露天习性的日变化

本研究旨在确定一天中的时间对开放场测试中习惯的影响，这是非联想海马依赖学习的最基本形式之一。在开始（08:30-10:00 h；定义为 Zeitgeber 时间（ZT）ZT0.5-2）、中期（13:00-14:30）对年轻的成年雄性 Wistar 大鼠进行旷场试验h, ZT5-6.5) 和光照期结束时 (18:30-20:00 h, ZT10.5-12)。我们的结果显示，在收购试验中，通过测试期间记录的六个参数之间没有显着差异。相比之下，行走和饲养的习惯水平上升如下：ZT0.5-2 < ZT10.5-12 < ZT5-6.5。在这两个试验中，主成分分析突出了两个成分：成分 1 主要由外区和内区的走动加载，饲养和冷冻行为，而组件 2 主要用于梳理活动和排便。参数之间的相关性在一天和试验期间各不相同。在获得试验中表现出更高水平的梳理、排便 (ZT5-6.5) 和冷冻行为 (ZT0.5-2 和 ZT5-6.5) 的动物在保留试验中更好地适应这些参数。总之，野外测试的习惯结果和测试参数之间的相关性高度依赖于白天。5）在获取试验中更好地习惯于保留试验中的这些参数。总之，野外测试的习惯结果和测试参数之间的相关性高度依赖于白天。5）在获取试验中更好地习惯于保留试验中的这些参数。总之，野外测试的习惯结果和测试参数之间的相关性高度依赖于白天。