Facciol Amanda, Tran Steven, Gerlai Robert
University of Toronto Mississauga, Department of Psychology, Canada.
University of Toronto, Department of Cell and Systems Biology, Canada.
Behav Brain Res. 2017 Jun 1;327:21-28. doi: 10.1016/j.bbr.2017.03.040. Epub 2017 Mar 27.
The light-dark preference test has been extensively used to screen anxiolytic drugs and investigate mechanisms of anxiety with rodents. Recently, this task has been adapted to zebrafish, but a number of inconsistent findings have emerged. For example, some found zebrafish to avoid and others to prefer dark. Given the translational relevance of the zebrafish, its utility in high throughput drug screens, and that anxiety still represents a large unmet medical need, there is an urgent need to resolve these inconsistencies. We propose these inconsistencies are due to lack of distinction between two separate factors: background shade and level of illumination. Here, we systematically manipulated background shade (black vs. white) while keeping the illumination level constant (uniformly illuminated). We also manipulated the level of illumination (illuminated vs. not illuminated) while keeping the background constant (either uniformly black or white). We examined the time-course of numerous behavioural responses under these conditions, and found zebrafish to exhibit a significant preference for the black side of the tank within the first 3min of the test when the illumination level was constant. We found this response, along with other anxiety-like behaviours, to diminish over time. In contrast, we found zebrafish did not exhibit a preference for the unilluminated (dark) side of the tank when the background shade was kept constant. Our results demonstrate a dissociation between illumination level and background shade, shown by a preference for black to white, but not for dark to light, confirming the importance of differentiating these two distinct factors.
明暗偏好测试已被广泛用于筛选抗焦虑药物，并在啮齿动物中研究焦虑机制。最近，该测试已适用于斑马鱼，但出现了一些不一致的结果。例如，一些研究发现斑马鱼会避开黑暗，而另一些则发现它们更喜欢黑暗。鉴于斑马鱼在转化研究中的相关性、其在高通量药物筛选中的实用性，以及焦虑仍然是一个尚未得到满足的重大医疗需求，迫切需要解决这些不一致之处。我们认为这些不一致是由于缺乏对两个独立因素的区分：背景颜色深浅和光照水平。在此，我们在保持光照水平恒定（均匀照明）的同时，系统地操纵背景颜色深浅（黑色与白色）。我们还在保持背景恒定（均匀黑色或白色）的同时，操纵光照水平（有光照与无光照）。我们检查了在这些条件下多种行为反应的时间进程，发现在光照水平恒定时，斑马鱼在测试的前3分钟内对鱼缸的黑色一侧表现出显著偏好。我们发现这种反应以及其他类似焦虑的行为会随着时间减弱。相比之下，当背景颜色深浅保持恒定时，我们发现斑马鱼对鱼缸未照明（黑暗）一侧没有表现出偏好。我们的结果表明了光照水平和背景颜色深浅之间的分离，表现为对黑色而非白色的偏好，但不是对黑暗而非光明的偏好，证实了区分这两个不同因素的重要性。
