Hoffman Emma, Pickavance Lucy, Thippeswamy Thimmasettappa, Beynon Robert J, Hurst Jane L
Mammalian Behaviour and Evolution Group, Institute of Integrative Biology, University of Liverpool, Leahurst Campus Neston, UK.
School of Veterinary Science, University of Liverpool Liverpool, UK.
Front Behav Neurosci. 2015 Apr 29;9:106. doi: 10.3389/fnbeh.2015.00106. eCollection 2015.
The integration of newly generated neurons persists throughout life in the mammalian olfactory bulb and hippocampus, regions involved in olfactory and spatial learning. Social cues can be potent stimuli for increasing adult neurogenesis; for example, odors from dominant but not subordinate male mice increase neurogenesis in both brain regions of adult females. However, little is known about the role of neurogenesis in social recognition or the assessment of potential mates. Dominant male mice scent-mark territories using urine that contains a number of pheromones including darcin (MUP20), a male-specific major urinary protein that stimulates rapid learned attraction to the spatial location and individual odor signature of the scent owner. Here we investigate whether exposure to darcin stimulates neurogenesis in the female brain. Hippocampal neurons and cellular proliferation in the lateral ventricles that supply neurons to the olfactory bulbs increased in females exposed for 7 days to male urine containing at least 0.5 μg/μl darcin. Darcin was effective whether presented alone or in the context of male urine, but other information in male urine appeared to modulate the proliferative response. When exposed to urine from wild male mice, hippocampal proliferation increased only if urine was from the same individual over 7 days, suggesting that consistency of individual scent signatures is important. While 7 days exposure to male scent initiated the first stages of increased neurogenesis, this caused no immediate increase in female attraction to the scent or in the strength or robustness of spatial learning in short-term conditioned place preference tests. The reliable and consistent stimulation of neurogenesis by a pheromone important in rapid social learning suggests that this may provide an excellent model to explore the relationship between the integration of new neurons and plasticity in spatial and olfactory learning in a socially-relevant context.
新生神经元的整合在哺乳动物的嗅球和海马体中持续终生，这两个区域参与嗅觉和空间学习。社会线索可能是促进成体神经发生的有力刺激因素；例如，来自占主导地位而非从属地位的雄性小鼠的气味会增加成年雌性小鼠这两个脑区的神经发生。然而，关于神经发生在社会识别或潜在配偶评估中的作用，我们知之甚少。占主导地位的雄性小鼠会用尿液标记领地，尿液中含有多种信息素，包括达辛（MUP20），这是一种雄性特异性主要尿蛋白，能刺激对气味所有者的空间位置和个体气味特征产生快速的习得性吸引力。在这里，我们研究接触达辛是否会刺激雌性大脑中的神经发生。在暴露于含有至少0.5μg/μl达辛的雄性尿液7天的雌性小鼠中，海马神经元以及向嗅球供应神经元的侧脑室中的细胞增殖有所增加。无论单独呈现还是在雄性尿液的背景下，达辛都有效果，但雄性尿液中的其他信息似乎会调节增殖反应。当暴露于野生雄性小鼠的尿液时，只有当尿液来自同一个体且持续7天时，海马增殖才会增加，这表明个体气味特征的一致性很重要。虽然暴露于雄性气味7天启动了神经发生增加的第一阶段，但在短期条件性位置偏好测试中，这并没有立即增加雌性对该气味的吸引力，也没有增强空间学习的强度或稳健性。一种在快速社会学习中起重要作用的信息素对神经发生的可靠且一致的刺激表明，这可能为探索在社会相关背景下新神经元的整合与空间和嗅觉学习可塑性之间的关系提供一个极佳的模型。
