美国芝加哥市Rosalind Franklin医学及科学大学的研究人员日前表示，他们在小鼠实验中发现，受到过某种精神刺激，例如受到大老鼠欺负的小鼠，大脑内产生的压力会导致新生的神经细胞死亡，甚至导致产生忧郁的情绪。研究人员表示，这项发现有助于治疗人类的忧郁症。
研究显示，受到欺负的小鼠大脑内关键的记忆和情绪区域也会产生新的神经细胞，但由于其承受巨大的压力，导致大多数细胞死亡。研究作者之一Daniel Peterson表示，如果可以想办法帮助小鼠大脑中新生的神经细胞存活下来，我们就可以助其遏止忧郁情绪的出现。
在这项研究中，研究人员将一只小鼠和两只大的小鼠关在一个笼子里20分钟，这段时间里，大老鼠很快就占了上风，它们不停地追咬小老鼠，小老鼠变得很害怕，情绪也很低落，分析显示这时小老鼠体内的压力荷尔蒙，是其它没有这种经历的小老鼠的7倍。
当他们对小鼠的大脑进行详细扫描后发现，仍然有新的细胞生成，但一周之后这些新细胞中仅有三分之一的细胞存活了下来。这意味着如果想帮助小老鼠避免新生细胞全部死亡，还有一段时间可以进行治疗。
研究人员接着计划找出可以保护新生神经细胞的药物，不过现在市场上大多数抗忧郁药，需要几周的时间才能生效，所以对保护新生细胞的功效可能不大。
(资料来源 : Bio.com)
原始出处：
Stress and Nerve Cells Survival in Rats; Finding may Open Window for Depression Treatment
03/14/07 -- A single, socially stressful situation can kill off new nerve cells in the brain region that processes learning, memory, and emotion, and possibly contribute to depression, new animal research shows.
Researchers found that in young rats, the stress of encountering aggressive, older rats did not stop the generation of new nerve cells?the first step in the process of neurogenesis. But stress did prevent the cells, located in the hippocampus, from surviving, leaving fewer new neurons for processing feelings and emotions. The hippocampus is one of two regions of the brain that continues to develop new nerve cells throughout life, in both rats and humans. The reduction of neurogenesis could be one cause of depression, says senior author Daniel Peterson, PhD, of the Rosalind Franklin University of Medicine and Science, near Chicago. His team reports their findings in the March 14 issue of The Journal of Neuroscience.
"This is strong evidence that the effects of social stress on neurogenesis occur after a delay of 24 hours or more, providing a possible time window for treatment after acute episodes of stress," says Henriette van Praag, PhD, of the Salk Institute for Biological Studies.
When Peterson and his research team put a young rat in a cage with two older rats for 20 minutes, the resident rats quickly pinned down and, in many cases, bit the intruder. The team reported that intruder rats were fearful and acted depressed around the bigger, more mature animals and had stress hormone levels six times as high as young rats that didn't experience a stressful encounter.
Examining the rats' brains under a microscope, the scientists discovered that even with high levels of stress hormones, the young, stressed rats generated as many new cells as their unstressed counterparts. Previous research had led some to think that hormone levels played a role in blocking the generation of new cells or caused them to die early on. But a week after the encounter, the team found that only a third of the cells generated under stress had survived. Long-term survival of nerve cells was also compromised: When Peterson's team marked newborn cells in the hippocampus, subjected rats to stress a week later, then examined brain tissue at the end of a month, they counted a third fewer fully developed nerve cells.
"The next step is to understand how stress reduced this survival," says Peterson. "We want to determine if anti-depressant medications might be able to keep these vulnerable new neurons alive."
Source: Society for Neuroscience
