2010年3月25日，NIBS所羅敏敏實(shí)驗(yàn)室在《Neuron》雜志發(fā)表最新文章。該文首次直接比較了嗅感覺神經(jīng)元與其對(duì)應(yīng)的嗅球投射神經(jīng)元對(duì)氣味信息的表征方式,，探討了嗅球的信號(hào)處理機(jī)制。
在自然界中存在成千上萬(wàn)種氣味分子,，動(dòng)物對(duì)這些氣味分子有著驚人的識(shí)別能力,。鼻腔中的嗅上皮內(nèi)的嗅感覺神經(jīng)元表達(dá)上千種氣味受體，而表達(dá)同種氣味受體的嗅感覺神經(jīng)元投射到嗅球表面相同的嗅小球中,，與特定的嗅球投射神經(jīng)元僧帽/叢狀細(xì)胞形成形成興奮性突觸性連接,。在嗅覺系統(tǒng)中的一個(gè)重要而具爭(zhēng)論性的問題是，嗅球中的投射神經(jīng)元怎樣編碼感覺神經(jīng)元向其傳遞的嗅覺信號(hào),。為回答這一問題,，本研究小組通過在定點(diǎn)基因轉(zhuǎn)入的小鼠中進(jìn)行電生理記錄和雙光子成像，首次比較了和同一受體（I7）相對(duì)應(yīng)的嗅感覺神經(jīng)元及其突觸后的僧帽/叢狀細(xì)胞對(duì)氣味的反應(yīng),。發(fā)現(xiàn)I7嗅感覺神經(jīng)元和I7僧帽/叢狀細(xì)胞在氣味濃度較低時(shí)表現(xiàn)出一致的氣味選擇性,。
氣味濃度增加時(shí)，I7嗅感覺神經(jīng)元和僧帽/叢狀細(xì)胞的氣味感受域會(huì)變寬,，但對(duì)醛類分子仍然具有選擇性,。來(lái)自不同個(gè)體的I7僧帽/叢狀細(xì)胞，其氣味感受域具有很高的保守性,。與投射神經(jīng)元不同的是,，嗅球內(nèi)的中間神經(jīng)元，包括球周細(xì)胞和顆粒細(xì)胞,，選擇性都比較低,。I7球周細(xì)胞的氣味感受域還出現(xiàn)了一定程度的異質(zhì)性。在氣味濃度較高時(shí),，阻斷嗅球內(nèi)的抑制性突觸傳遞會(huì)降低僧帽/叢狀細(xì)胞的選擇性,。在氣味濃度較低時(shí)則沒有這種作用。這一研究結(jié)果顯示,，嗅球中投射神經(jīng)元的氣味選擇性主要由其前一級(jí)對(duì)應(yīng)的氣味受體決定,，而嗅球中的中間神經(jīng)元通過側(cè)向抑制的作用銳化投射神經(jīng)元的調(diào)諧曲線。
博士生譚潔為本文的第一作者,，文章的其他作者還有賓夕法尼亞大學(xué)的馬明紅博士和Agnès Savigner博士,，羅敏敏博士為本文的通訊作者。此項(xiàng)研究由科技部863及973計(jì)劃,，北京市科委,，中國(guó)自然科學(xué)基金及人類前沿科學(xué)計(jì)劃（HFSP） 資助，在北京生命科學(xué)研究所完成,。(生物谷Bioon.com)
生物谷推薦原文出處：
Neuron doi:10.1016/j.neuron.2010.02.011
Odor Information Processing by the Olfactory Bulb Analyzed in Gene-Targeted Mice
Jie Tan1, 2, Agnès Savigner3, Minghong Ma3 and Minmin Luo2, 4
1 Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China
2 National Institute of Biological Sciences, Beijing 102206, China
3 Department of Neuroscience, University of Pennsylvania School of Medicine, Philadelphia, PA 19104, USA
4 School of Life Sciences, Tsinghua University, Beijing 100084, China
In mammals, olfactory sensory neurons (OSNs) expressing a specific odorant receptor (OR) gene project with precise stereotypy onto mitral/tufted (M/T) cells in the main olfactory bulb (MOB). It remains challenging to understand how incoming olfactory signals are transformed into outputs of M/T cells. By recording from OSNs expressing mouse I7 receptor and their postsynaptic neurons in the bulb, we found that I7 OSNs and their corresponding M/T cells exhibit similarly selective tuning profiles at low concentrations. Increasing the concentration significantly reduces response selectivity for both OSNs and M/T cells, although the tuning curve of M/T cells remains comparatively narrow. By contrast, interneurons in the MOB are broadly tuned, and blocking GABAergic neurotransmission reduces selectivity of M/T cells at high odorant concentrations. Our results indicate that olfactory information carried by an OR is channeled to its corresponding M/T cells and support the role of lateral inhibition via interneurons in sharpening the tuning of M/T cells.
