Parolisi Roberta, Cozzi Bruno, Bonfanti Luca
Neuroscience Institute Cavalieri Ottolenghi (NICO), Orbassano, Italy.
Department of Veterinary Sciences, University of Turin, Via Leonardo da Vinci, 44, 10095, Grugliasco, TO, Italy.
Brain Struct Funct. 2017 Aug;222(6):2625-2639. doi: 10.1007/s00429-016-1361-3. Epub 2017 Feb 25.
Adult neurogenesis has been implicated in brain plasticity and brain repair. In mammals, it is mostly restricted to specific brain regions and specific physiological functions. The function and evolutionary history of mammalian adult neurogenesis has been elusive so far. The largest neurogenic site in mammals (subventricular zone, SVZ) generates neurons destined to populate the olfactory bulb. The SVZ neurogenic activity appears to be related to the dependence of the species on olfaction since it occurs at high rates throughout life in animals strongly dependent on this function for their survival. Indeed, it dramatically decreases in humans, who do not depend so much on it. This study investigates whether the SVZ neurogenic site exists in mammals devoid of olfaction and olfactory brain structures, such as dolphins. Our results demonstate that a small SVZ-like region persists in these aquatic mammals. However, this region seems to have lost its neurogenic capabilities since neonatal stages. In addition, instead of the typical newly generated neuroblasts, some mature neurons were observed in the dolphin SVZ. Since cetaceans evolved from terrestrial ancestors, non-neurogenic SVZ may indicate extinction of adult neurogenesis in the absence of olfactory function, with the retention of an SVZ-like anatomical region either vestigial or of still unknown role.
成年神经发生与脑可塑性和脑修复有关。在哺乳动物中，它主要局限于特定的脑区和特定的生理功能。到目前为止，哺乳动物成年神经发生的功能和进化史一直难以捉摸。哺乳动物中最大的神经发生部位（脑室下区，SVZ）产生注定要迁入嗅球的神经元。SVZ的神经发生活动似乎与物种对嗅觉的依赖有关，因为在强烈依赖这种功能生存的动物中，它在整个生命过程中都以很高的速率发生。事实上，在不太依赖嗅觉的人类中，它会显著减少。本研究调查了在没有嗅觉和嗅脑结构的哺乳动物，如海豚中，是否存在SVZ神经发生部位。我们的结果表明，在这些水生哺乳动物中存在一个小的类似SVZ的区域。然而，这个区域似乎从新生儿阶段就失去了神经发生能力。此外，在海豚的SVZ中，观察到的不是典型的新生成的神经母细胞，而是一些成熟神经元。由于鲸类动物是从陆地祖先进化而来的，非神经发生的SVZ可能表明在没有嗅觉功能的情况下成年神经发生已经消失，同时保留了一个类似SVZ的解剖区域，其作用要么是退化的，要么仍然未知。
