哺乳动物成体神经元的再生:内、外环境因子的作用

哺乳动物成体神经元的再生现象是最近三十年才被科学家们所认识并逐渐接受的。随着科研方法与实验技术的发展，在成年哺乳动物的一些特定脑区，比如海马齿状回(Dentate gyrus of the hippocampus)、室下区(Subventricular zone)和杏仁核(Amygdala)中发现了新生细胞。研究表明，内外环境因子可影响成体神经元的再生。具体表现在环境多样性、自主活动、有益社会交往、短日光照、化学刺激以及诸如5—羟色胺和脑源性神经营养因子等神经递质水平的增加，都会促进新生细胞的增生或存活。而负面社会交往及应激激素皮质酮对成体神经元的再生有抑制和降低作用。研究还表明，根据种和性别的差异，类脂醇激素对成体神经元的再生起到促进或抑制作用。最新的实验证实新生细胞在成体中具有显著功能[动物学报49(2)：151—162，2003]。

Adult neurogenesis in the mammalian brain: exogenous and endogenous influences

Until the past three decades, the general scientific community did not regard adult mammalian neurogenesis as an actual phenomenon. However, with th e advent of new scientific methods and techniques, researchers have been able to identify and characterize new cells proliferating in several brain regions, inc luding the dentate gyrus of the hippocampus, subventricular zone, and amygdala. Recently, studies have provided evidence that environmental factors, both exter nal and internal, may influence adult neurogenesis. Specifically, the addition and/or survival of newly proliferated cells in various regions of the adult brai n may be increased by environmental enrichment, voluntary activity, positive soc ial interactions, short day length, chemosensory stimuli, or increased levels o f neurotransmitters including serotonin and brain derived neurotrophic factor. A dult neurogenesis may be inhibited/decreased by negative social interactions or the stress hormone corticosterone. Interestingly, gonadal steroid hormones may exert positive or negative effects depending on the species and sex of the anima l. Finally, current evidence supports the contention that these new cells do be come functionally significant in the adult brain