Shieh Kun-Ruey, Yang Shu-Chuan
Department of Physiology, Tzu Chi University, Hualien 970, Taiwan.
Holistic Education Center, Tzu Chi University of Science and Technology, Hualien 970, Taiwan
J Exp Biol. 2019 Sep 18;222(Pt 18):jeb199356. doi: 10.1242/jeb.199356.
Taiwan is a mountainous island, and nearly 75% of its lands are 1000 m above sea level. Formosan wood mice, , are endemic rodents and are broadly distributed at altitudes between 1400 and 3700 m in Taiwan. Interestingly, Formosan wood mice show similar locomotor activity in the laboratory as they do in the wild. Hence, we are interested in studying whether exploratory behaviors and central dopaminergic activity are changed in the open field test. We used male C57BL/6J mice as the control, comparing their behavioral responses in the open field, step-down inhibitory avoidance discrimination and novel object recognition tests with those of male Formosan wood mice. We also examined dopamine and its major metabolite 3,4-dihydroxyphenylacetic acid in the medial prefrontal cortex, striatum and nucleus accumbens. In open field tests, Formosan wood mice revealed higher levels of locomotion and exploration than C57BL/6J mice. Learning and memory performance in the novel object recognition test was similar in both Formosan wood mice and C57BL/6J mice, but more agile responses in the inhibitory avoidance discrimination task were found in Formosan wood mice. There was no difference in behavioral responses in the open field test between new second-generation Formosan wood mice and Formosan wood mice that were inbred for more than 10 generations. After repeated exposure to the open field test, high levels of locomotion and exploration as well as central dopaminergic activities were markedly persistent in Formosan wood mice, but these activities were significantly reduced in C57BL/6J mice. Diazepam (anxiolytic) treatment reduced the higher exploratory activity and central dopaminergic activities in Formosan wood mice, but this treatment had no effect in C57BL/6J mice. This study provides comparative findings, as two phylogenetically related species showed differences in behavioral responses.
台湾是一个多山的岛屿，其近75%的土地海拔在1000米以上。台湾森鼠是台湾特有的啮齿动物，广泛分布于台湾海拔1400至3700米之间。有趣的是，台湾森鼠在实验室中的运动活动与在野外时相似。因此，我们有兴趣研究在旷场试验中探索行为和中枢多巴胺能活性是否发生了变化。我们以雄性C57BL/6J小鼠作为对照，将它们在旷场试验、跳台抑制性回避辨别试验和新物体识别试验中的行为反应与雄性台湾森鼠的行为反应进行比较。我们还检测了内侧前额叶皮质、纹状体和伏隔核中的多巴胺及其主要代谢产物3,4-二羟基苯乙酸。在旷场试验中，台湾森鼠的运动和探索水平高于C57BL/6J小鼠。在新物体识别试验中，台湾森鼠和C57BL/6J小鼠的学习和记忆表现相似，但在抑制性回避辨别任务中，台湾森鼠的反应更敏捷。新的第二代台湾森鼠与近亲繁殖超过10代的台湾森鼠在旷场试验中的行为反应没有差异。在反复进行旷场试验后，台湾森鼠的高水平运动、探索以及中枢多巴胺能活性明显持续存在，但这些活性在C57BL/6J小鼠中显著降低。地西泮（抗焦虑药）治疗降低了台湾森鼠较高的探索活性和中枢多巴胺能活性，但该治疗对C57BL/6J小鼠没有影响。这项研究提供了比较结果，因为两个系统发育相关的物种在行为反应上表现出差异。
