Density-dependent change in aggressive behavior contributes to the population regulation of many small rodents, but the underlying neurological mechanisms have not been examined in field conditions. We hypothesized that crowding stress and aggression-associated oxytocin (OT) and arginine vasopressin (AVP) in specific regions of the brain may be closely related to aggressive behaviors and population changes of small rodents. We analyzed the association of OT and AVP expression, aggressive behavior, and population density of Brandt’s voles in 24 large semi-natural enclosures (0.48 ha each) in Inner Mongolia grassland. We tested the effects of population density on the OT/AVP system and aggressive behavior by experimentally manipulating populations of Brandt’s voles in the grassland enclosures. High density was positively and significantly associated with more aggressive behavior, and increased expression of mRNA and protein of AVP and its receptor, but decreased expression of mRNA and protein of OT and its receptor in specific brain regions of the voles. Our study suggests that changes in OT/AVP expression are likely a result of the increased psychosocial stress that these voles experience during overcrowding, and thus the OT/AVP system can be used as indicators of density-dependent stressors in Brandt’s voles.

中文翻译：

---

种群变异改变了野外条件下布兰特田鼠大脑中与攻击相关的催产素和加压素的表达

攻击行为的密度依赖性变化有助于许多小型啮齿动物的种群调节，但尚未在野外条件下检查潜在的神经机制。我们假设大脑特定区域的拥挤压力和攻击相关的催产素 (OT) 和精氨酸加压素 (AVP) 可能与小型啮齿动物的攻击行为和种群变化密切相关。我们分析了内蒙古草原 24 个大型半自然围栏（每个 0.48 公顷）中布兰特田鼠 OT 和 AVP 表达、攻击行为和种群密度的关联。我们通过实验操纵草地围栏中的布兰特田鼠种群来测试种群密度对 OT/AVP 系统和攻击行为的影响。高密度与更具攻击性的行为呈显着正相关，AVP及其受体的mRNA和蛋白质表达增加，但田鼠特定脑区的OT及其受体mRNA和蛋白质的表达降低。我们的研究表明 OT/AVP 表达的变化可能是这些田鼠在过度拥挤期间经历的心理社会压力增加的结果，因此 OT/AVP 系统可用作 Brandt 田鼠密度依赖性压力源的指标。