Bai Yiming, Liu Harrison, Huang Bo, Wagle Mahendra, Guo Su
State Key Laboratory of Genetic Engineering, Department of Genetics, School of Life Sciences, Fudan University, Shanghai, China.
Graduate Program in Bioengineering, University of California, San Francisco, CA, USA.
BMC Neurosci. 2016 Sep 15;17(1):63. doi: 10.1186/s12868-016-0298-z.
Larval zebrafish, with a simple and transparent vertebrate brain composed of 100 K neurons, is well suited for deciphering entire neural circuit activity underlying behavior. Moreover, their small body size (4-5 mm in length) is compatible with 96-well plates, making larval zebrafish amenable to high content screening. Despite these attractive features, there is a scarcity of behavioral characterizations in larval zebrafish compared to other model organisms as well as adult zebrafish.
In this study, we have characterized the physiological and behavioral responses of larval zebrafish to several easily amenable stimuli, including heat, cold, UV, mechanical disturbance (MD), and social isolation (SI). These stimuli are selected based on their perceived aversive nature to larval zebrafish. Using a light/dark choice paradigm, in which larval zebrafish display an innate dark avoidance behavior (i.e. scotophobia), we find that heat, cold and UV stimuli significantly enhance their dark avoidance with heat having the most striking effect, whereas MD and SI have little influence on the behavior. Surprisingly, using the cortisol assay, a physiological measure of stress, we uncover that all stimuli but heat and SI significantly increase the whole body cortisol levels.
These results identify a series of stressors that can be easily administered to larval zebrafish. Those stimuli that elicit differential responses at behavioral and physiological levels warrant further studies at circuit levels to understand the underlying mechanisms. The findings that various stressors enhance while anxiolytics attenuate dark avoidance further reinforce that the light/dark preference behavior in larval zebrafish is fear/anxiety-associated.
斑马鱼幼体拥有一个由约10万个神经元组成的简单且透明的脊椎动物大脑，非常适合用于解读行为背后的整个神经回路活动。此外，它们的体型较小（体长约4 - 5毫米），适合在96孔板中饲养，这使得斑马鱼幼体便于进行高内涵筛选。尽管具有这些吸引人的特征，但与其他模式生物以及成年斑马鱼相比，斑马鱼幼体的行为特征研究较少。
在本研究中，我们对斑马鱼幼体对几种易于施加的刺激（包括热、冷、紫外线、机械干扰（MD）和社会隔离（SI））的生理和行为反应进行了特征描述。这些刺激是根据它们被认为对斑马鱼幼体具有厌恶性质而选择的。使用明暗选择范式，即斑马鱼幼体表现出天生的暗回避行为（即畏暗症），我们发现热、冷和紫外线刺激显著增强了它们的暗回避行为，其中热的影响最为显著，而MD和SI对该行为影响较小。令人惊讶的是，通过皮质醇测定（一种压力的生理指标），我们发现除热和SI外，所有刺激均显著提高了全身皮质醇水平。
这些结果确定了一系列可以轻松施加于斑马鱼幼体的应激源。那些在行为和生理水平上引发不同反应的刺激值得在神经回路水平上进一步研究，以了解其潜在机制。各种应激源增强而抗焦虑药物减弱暗回避行为的发现进一步强化了斑马鱼幼体的明暗偏好行为与恐惧/焦虑相关的观点。
