生物谷報道：近期的證據(jù)表明抗抑郁劑可以促使成熟的海馬（掌管記憶的大腦區(qū)域）中形成新的神經(jīng)元,。這些發(fā)現(xiàn)激起了人們對成熟神經(jīng)發(fā)生的興趣,，并且也提出了這樣一個問題：新神經(jīng)元也能在成熟大腦中與思考和情緒混亂（抑郁和焦慮）有關(guān)的區(qū)域中萌發(fā),。
現(xiàn)在,，來自美國國家衛(wèi)生研究院（NIH）的智力健康研究院（NIMH）的研究人員在成熟的大鼠皮層中發(fā)現(xiàn)了通過神經(jīng)遞質(zhì)GABA（gamma-aminobutyric acid）（一種能夠抑制神經(jīng)元活動的神經(jīng)遞質(zhì)）來交流的新生神經(jīng)元,。在皮層中,，這種新神經(jīng)元似乎源自本地的,、先前未知的前體細胞,，而不是由從其他地方遷移來的細胞形成。研究人員將這些發(fā)現(xiàn)公布在2005年1月31日的Journal of Cell Biology(JCB)上,。
NIMH研究組利用了更多的標(biāo)記物來追蹤新生的神經(jīng)元并且確定出它們分泌的神經(jīng)遞質(zhì)的類型,。這些標(biāo)記物利用抗體對特定蛋白的親和力使特殊的細胞類型帶上指示顏色密碼。研究人員發(fā)現(xiàn)大鼠大腦皮層和紋狀體正在產(chǎn)生新的,、廣泛散布的小細胞即中間神經(jīng)元,。這種神經(jīng)元能夠制造和分泌GABA。這種新的中間神經(jīng)元與海馬和嗅球中的細胞很相似,，并且產(chǎn)生的頻率也相似,。中間神經(jīng)元被認為在調(diào)節(jié)較大類型的神經(jīng)元中起到一定的作用。
由于抗抑郁劑能夠促進成熟海馬區(qū)域的神經(jīng)形成,，因此它們可能對皮層有相似的作用,。但是有關(guān)新神經(jīng)元的調(diào)節(jié)和可能的功能問題還有待進一步研究.
JCB在本期也給出了精彩的評論，全文如下：
Neurogenesis in the adult brain is generally considered to be restricted to the hippocampus and olfactory bulb—ancient parts of the brain that are found even in nonmammalian species. A few publications suggested that the neocortex—a well-developed region in primates that is implicated in higher thought—also supports neurogenesis. These reports have been met with skepticism, as other groups have been unable to replicate the findings. On page 415, Dayer et al. bolster the evidence for proliferating neurons in regions beyond the hippocampus and olfactory bulb.The authors used a battery of neuronal markers to confirm that neurogenesis exists in the neocortex. Although difficult to find in the sparsely populated expanse of the cortex, replicating cells with markers of neuronal precursors were present in the adult rat neocortex. Their numbers suggest that these interneurons in the cortex turnover as rapidly as granule cells in the hippocampus, where up to 6% of the cells are replaced within a month.
The various markers that the authors used also revealed for the first time that the neocortical precursors produce GABAergic interneurons, which are small inhibitory neurons that regulate the larger pyramidal cells of the cortex. Because most neurons in the cortex are pyramidal cells, which are large and unmistakably neuronal, the new interneurons can be easily overlooked or mistaken for glial cells.
The precursors originate from within the cortex itself, rather than migrating from the subventricular zone (SVZ), which provides new neurons to the olfactory bulb. The authors did note, however, that some SVZ precursors also found their way to the striatum—a region associated with motor skill learning—where they formed interneurons.
Depression has been correlated with decreased hippocampal neurogenesis and a decrease in small cells in the neocortex that look like glia. The new findings hint that some of those missing cells may be newly born interneurons and suggest that neurogenesis in the cortex will be an important event to examine in disease states and old age.
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