Division of Systems Medical Science, Institute for Comprehensive Medical Science, Fujita Health University, Toyoake, Aichi, 470-1192, Japan.
Mol Brain. 2021 Feb 15;14(1):34. doi: 10.1186/s13041-020-00721-2.
The elevated plus maze test is a widely used test for assessing anxiety-like behavior and screening novel therapeutic agents in rodents. Previous studies have shown that a variety of internal factors and procedural variables can influence elevated plus maze behavior. Although some studies have suggested a link between behavior and plasma corticosterone levels, the relationships between them remain unclear. In this study, we investigated the effects of experience with a battery of behavioral tests, the wall color of the closed arms, and illumination level on the behavior and plasma corticosterone responses in the elevated plus maze in male C57BL/6J mice. Mice were either subjected to a series of behavioral tests, including assessments of general health and neurological function, a light/dark transition test, and an open field test, or left undisturbed until the start of the elevated plus maze test. The mice with and without test battery experience were allowed to freely explore the elevated plus maze. The other two independent groups of naïve mice were tested in mazes with closed arms with different wall colors (clear, transparent blue, white, and black) or different illumination levels (5, 100, and 800 lx). Immediately after the test, blood was collected to measure plasma corticosterone concentrations. Mice with test battery experience showed a lower percentage of open arm time and entries and, somewhat paradoxically, had lower plasma corticosterone levels than the mice with no test battery experience. Mice tested in the maze with closed arms with clear walls exhibited higher open arm exploration than mice tested in the maze with closed arms with black walls, while there were no significant differences in plasma corticosterone levels between the different wall color conditions. Illumination levels had no significant effects on any measure. Our results indicate that experience with other behavioral tests and different physical features of the maze affect elevated plus maze behaviors. Increased open arm time and entries are conventionally interpreted as decreased anxiety-like behavior, while other possible interpretations are considered: open arm exploration may reflect heightened anxiety and panic-like reaction to a novel situation under certain conditions. With the possibility of different interpretations, the present findings highlight the need to carefully consider the test conditions in designing experiments and drawing conclusions from the behavioral outcomes in the elevated plus maze test in C57BL/6J mice.
高架十字迷宫测试是一种广泛用于评估焦虑样行为和筛选新治疗剂的啮齿动物测试方法。先前的研究表明，多种内部因素和程序变量会影响高架十字迷宫行为。尽管一些研究表明行为与血浆皮质酮水平之间存在关联，但它们之间的关系仍不清楚。在这项研究中，我们研究了一系列行为测试经验、闭臂壁颜色和照明水平对雄性 C57BL/6J 小鼠高架十字迷宫行为和血浆皮质酮反应的影响。将小鼠分为两组，一组接受一系列行为测试，包括一般健康和神经功能评估、明暗过渡测试和旷场测试，另一组则不受干扰，直到高架十字迷宫测试开始。有和没有测试套件经验的小鼠都可以自由探索高架十字迷宫。另外两组未经过测试的小鼠被测试在具有不同壁颜色（透明、透明蓝色、白色和黑色）或不同照明水平（5、100 和 800 lx）的迷宫中。测试后立即采集血液以测量血浆皮质酮浓度。有测试套件经验的小鼠在开放臂上的时间和进入次数百分比较低，而且有点矛盾的是，它们的血浆皮质酮水平低于没有测试套件经验的小鼠。在具有透明壁的闭臂迷宫中测试的小鼠比在具有黑色壁的闭臂迷宫中测试的小鼠表现出更高的开放臂探索，而不同壁颜色条件下的血浆皮质酮水平没有显著差异。照明水平对任何测量值都没有显著影响。我们的结果表明，其他行为测试经验和迷宫的不同物理特征会影响高架十字迷宫行为。开放臂时间和进入次数的增加通常被解释为焦虑样行为减少，而其他可能的解释是：在某些条件下，开放臂探索可能反映出对新情况的高度焦虑和恐慌样反应。由于存在不同的解释，因此目前的发现强调了在设计实验和从 C57BL/6J 小鼠的高架十字迷宫测试中得出行为结果时，需要仔细考虑测试条件并得出结论的必要性。
