Kiyokawa Yasushi, Honda Akira, Takeuchi Yukari, Mori Yuji
Laboratory of Veterinary Ethology, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan.
Behav Brain Res. 2014 Jul 1;267:189-93. doi: 10.1016/j.bbr.2014.03.043. Epub 2014 Mar 31.
In social animals, the presence of an affiliative conspecific alleviates acute stress responses, and this is called social buffering. We previously reported in male rats that the presence of a conspecific mitigates conditioned fear responses to auditory conditioned stimulus paired with foot shocks. Subsequent studies revealed that we could observe this social buffering when rats were tested in a box odorized by a conspecific. Because we previously used an unfamiliar conspecific, the effects of familiarity with a conspecific on the intensity of social buffering remain unclear. Here, we examine this question by preparing a familiar conspecific that had been housed with a subject for 3 weeks in the same cage. We exposed fear-conditioned subjects to a conditioned stimulus in either a clean control box or a box odorized beforehand by either an unfamiliar or a familiar conspecific. When the subjects were tested in the control box, they showed freezing and Fos expression in the paraventricular nucleus. These responses were suppressed when we placed rats in the box odorized by a conspecific. However, the suppression was greater when the box was odorized by a familiar conspecific rather than by an unfamiliar conspecific. Fos expression in the lateral amygdala was also suppressed in the same manner. These results suggest that a familiar conspecific is more effective for social buffering of conditioned fear responses.
在群居动物中，有一个亲和的同种个体存在可减轻急性应激反应，这被称为社会缓冲。我们之前在雄性大鼠中报道过，同种个体的存在可减轻对与足部电击配对的听觉条件刺激的条件性恐惧反应。随后的研究表明，当在被同种个体气味熏染的箱子中对大鼠进行测试时，我们能够观察到这种社会缓冲现象。由于我们之前使用的是不熟悉的同种个体，所以同种个体的熟悉程度对社会缓冲强度的影响仍不清楚。在这里，我们通过准备一个与受试动物在同一笼子里共同饲养3周的熟悉的同种个体来研究这个问题。我们将恐惧条件化的受试动物置于一个干净的对照箱中，或者置于一个事先被不熟悉或熟悉的同种个体气味熏染过的箱子中，使其接受条件刺激。当在对照箱中对受试动物进行测试时，它们在室旁核表现出僵住和Fos表达。当我们将大鼠置于被同种个体气味熏染的箱子中时，这些反应受到抑制。然而，当箱子被熟悉的同种个体而不是不熟悉的同种个体气味熏染时，这种抑制作用更强。杏仁核外侧的Fos表达也以同样的方式受到抑制。这些结果表明，熟悉的同种个体对条件性恐惧反应的社会缓冲更有效。
