Koizumi Ryoko, Kiyokawa Yasushi, Tanaka Kazuyuki D, Tanikawa Tsutomu, Takeuchi Yukari
Laboratory of Veterinary Ethology, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan.
Technical Research Laboratory, Ikari Shodoku Corporation, 1-12-3 Akanehama, Narashino-shi, Chiba 275-0024, Japan.
J Vet Med Sci. 2019 Aug 24;81(8):1121-1128. doi: 10.1292/jvms.19-0040. Epub 2019 Jul 2.
Wild animals tend to avoid novel objects that do not elicit clear avoidance behaviors in domesticated animals. We previously found that the basolateral complex of the amygdala (BLA) and dorsal bed nucleus of the stria terminalis (dBNST) were larger in trapped wild rats compared with laboratory rats. Based on these findings, we hypothesized that the BLA and/or dBNST would be differentially activated when wild and laboratory rats showed different avoidance behaviors towards novel objects. In this study, we placed novel objects at one end of the home cage. We measured the time spent in that half of the cage and expressed the data as a percentage of the time spent in that region with no object placement. We found that this percentage was lower in the wild rats compared with the laboratory rats. These behavioral differences were accompanied by increased Fos expression in the BLA, but not in the dBNST, of the wild rats. These results suggest that wild rats show greater BLA activation compared with laboratory rats in response to novel objects. We also found increased Fos expression in the paraventricular nucleus of the hypothalamus, ventral BNST, and ventromedial hypothalamus, but not in the central amygdala of wild rats. Taken together, our data represent new information regarding differences in behavioral and neural responses towards novel objects in wild vs. laboratory rats.
野生动物往往会避开那些在家养动物中不会引发明显回避行为的新奇物体。我们之前发现，与实验大鼠相比，被困野生大鼠的杏仁核基底外侧复合体（BLA）和终纹床核背侧部（dBNST）更大。基于这些发现，我们推测，当野生大鼠和实验大鼠对新奇物体表现出不同的回避行为时，BLA和/或dBNST会被差异性激活。在本研究中，我们将新奇物体放置在饲养笼的一端。我们测量了在笼子该半侧所花费的时间，并将数据表示为在没有放置物体的该区域所花费时间的百分比。我们发现，与实验大鼠相比，野生大鼠的这一百分比更低。这些行为差异伴随着野生大鼠BLA中Fos表达的增加，但dBNST中没有。这些结果表明，与实验大鼠相比，野生大鼠对新奇物体的反应表现出更强的BLA激活。我们还发现，野生大鼠下丘脑室旁核、腹侧终纹床核和下丘脑腹内侧核中Fos表达增加，但中央杏仁核中没有。综上所述，我们的数据代表了关于野生大鼠和实验大鼠对新奇物体的行为和神经反应差异的新信息。
