生物谷報(bào)道：2007年8月16日，北京生命科學(xué)研究所羅敏敏實(shí)驗(yàn)室在《Science》雜志上發(fā)表文章報(bào)道了小鼠可以通過一類特殊的嗅覺神經(jīng)元感受接近于空氣中濃度的二氧化碳,。
二氧化碳（CO2）對于許多生物是一種重要的環(huán)境信號分子,。傳統(tǒng)上二氧化碳被認(rèn)為是無色無味的氣體。經(jīng)典的心理物理學(xué)測試證明對于二氧化碳確實(shí)不能由人類的嗅覺系統(tǒng)所檢測,，但是其他的哺乳動物是否可以通過嗅覺系統(tǒng)感受低濃度的二氧化碳(空氣中二氧化碳平均濃度0.038%)仍然不清楚,。
由北京生命科學(xué)研究所羅敏敏研究員所領(lǐng)導(dǎo)的課題組運(yùn)用分子生物學(xué)、免疫組織化學(xué),、小鼠遺傳操作,、電生理、鈣成像,、以及行為學(xué)等多種實(shí)驗(yàn)手段,證明了小鼠能通過一類表達(dá)D型鳥苷酸環(huán)化酶（GC-D）的嗅覺感覺細(xì)胞感受接近于大氣中濃度的二氧化碳,。他們首先發(fā)現(xiàn)表明碳酸酐酶II,一種催化CO2與水生成HCO3-和H+的酶，特異地表達(dá)在這類GC-D神經(jīng)元中,。這些神經(jīng)元的軸突投射到嗅球中的項(xiàng)鏈嗅小球,，形成所謂的項(xiàng)鏈嗅覺系統(tǒng),。這一研究運(yùn)用鈣成像與電生理記錄表明CO2激活GC-D神經(jīng)元以及嗅球中與項(xiàng)鏈嗅小球聯(lián)系的神經(jīng)細(xì)胞,。行為學(xué)實(shí)驗(yàn)結(jié)果表明小鼠檢測CO2的閾限為0.066%,非常接近空氣中CO2的平均濃度（0.038%）。最后,，他們的藥理實(shí)驗(yàn)及行為實(shí)驗(yàn)證明小鼠這樣靈敏的二氧化碳檢測能力需要碳酸酐酶II的活性及環(huán)鳥苷酸環(huán)敏感的離子通道的開發(fā),。
這一研究首次證明二氧化碳可以被哺乳動物的嗅覺系統(tǒng)靈敏地檢測到,，并且此一檢測是通過項(xiàng)鏈嗅覺系統(tǒng)所完成，而此一特異的嗅覺系統(tǒng)的功能一直不清楚,。最后,，此一研究對于哺乳動物對CO2檢測的細(xì)胞機(jī)制提供了初步線索。
Fig. 1. CAII immunoreactivity in GC-D+ neurons and necklace glomeruli. (A) Bilaterally symmetric distribution of CAII+ cells (arrows) in the OE. (B) High-power view of CAII immunoreactivity in a CAII+ cluster. (C) PDE2A immunoreactivity in the same section as (B). (D) Overlay of (B) and (C). (E) Acoronal section of the caudal OB showing CAII+ glomeruli (arrows) with largely bilateral symmetry. (F) High-power view of CAII immunoreactivity within the dashed box in (E). (G) PDE2A immunoreactivity. (H) Overlay of (F) and (G). Blue, DAPI labeling. (I to K) CAII expression overlaps with GFP labeling in the OE of GCD-ITG mice. (I) CAII immunoreactivity. (J) GFP immunoreactivity within the same region as (I). (K) Overlay of (I) and (J). (L to N) CAII expression overlaps with GFP labeling in the OB of GCD-ITG mice. (L) CAII+ glomeruli. (M) GFP+ glomeruli within the same region as (L). (N) Overlay of (L) and (M). Scale bars in (B), 20 µm; (F), 100 µm; (I), 10 µm; and (L), 50 µm. [View Larger Version of this Image (368K JPEG file)]
原文出處：
Science 17 August 2007 Vol 317, Issue 5840
Detection of Near-Atmospheric Concentrations of CO2 by an Olfactory Subsystem in the Mouse
Ji Hu, Chun Zhong, Cheng Ding, Qiuyi Chi, Andreas Walz, Peter Mombaerts, Hiroaki Matsunami, and Minmin Luo
Science 17 August 2007: 953-957.
Mice can sense near-atmospheric concentrations of CO2 using a subset of olfactory neurons that may utilize the catabolic enzyme carbonic anhydrase.
Abstract »| Full Text »| PDF »| Supporting Online Material »|
作者簡介：
Dr. Minmin Luo’s Lab
Minmin Luo,Ph.D
Assistant Investigator, NIBS, Beijing, China
Research Description:
Our lab is focusing on two related neurobiology questions:
1. the encoding of olfactory signals in the mammalian brain;
2. the physiological mechanisms of innate social behaviors at the level of neural circuits.
Mammals can detect and discriminate infinite number of odorant chemicals. Over the last decade, dramatic progresses have been achieved in our understanding of the olfactory system. The work by Buck and Axel revealed that mammals possess over 1000 odorant receptors. Each olfactory sensory neuron expresses a single odorant receptor, and neurons of common receptors converge into one or two glomeruli in the the olfactory bulb, thus forming a topographic map at the level of odorant receptor. However, it remains unclear how odorants are encoded by the olfactory bulb. Our laboratory studies how neuronal activity in the olfactory bulb encode olfactory signals and then project to downstream stations, using approaches such as electrophysiology, optical imaging, and genetic engineering.
Some special odorants, such as the body odorants emanated by other conspecifics or predators, can be detected at especially low concentrations and effectively release specific behaviors, such as mating, aggression, or innate fears. A discrete neural pathway from the olfactory bulb to the hypothalamus via the medial amygdala detects these odorants and regulates the innate social behaviors. We are using approaches including electrophysiology, neural tract tracing, genetic engineering, and behavioral assay to study the representation of the olfactory signals in this pathway. We are testing the labeled-line hypothesis: whether some specialized receptor neurons and their directly connected central pathways respond selectively to subset of social signals and regulate specific behavior. We are also recording the intrinsic and synaptic properties of the neurons in this pathway from slice preparations to examine the physiological substrates for the representation of social signals. Many mental diseases manifest themselves as disorders of social behavior. Our studies thus not only have the potentials of contributing to the basic understanding of sensory processing and some most fundamental forms of social behaviors but also may facilitate clinical efforts toward the cure of these diseases.
Publications:
1. Luo M. and Katz L.C.. Encoding Pheromones by the Mammalian Vomeronasal System. Curr Opinion Neurobiol. 2004; 14:428-34.
2. Luo M.. Got milk? A pheromonal message for newborn rabbits. Bioessays. 2004; 26:6-9.
3. Luo M., Fee M.S., and Katz L.C.. Encoding pheromonal signals in the accessory olfactory bulb of behaving mice. Science. 2003; 299:1196-1201 (full research article featured with cover and News and Views).
4. Luo M. and Perkel D.J.. Intrinsic properties and synaptic input for neurons within an avian motor thalamic nucleus during the phase crucial for song learning. J Neurophysiol. 2002; 88:1903-1914.
5. Perkel D.J., Farries M.A., Luo M., and Ding L. Electrophysiological analysis of a songbird basal ganglia circuit essential for vocal plasticity. Brain Res Bulletin. 2002; 57:529-532 (Invited review).
6. Luo M. and Katz L.C.. Response correlation maps of neurons in the mammalian olfactory bulb. Neuron. 2001; 32:1165-1179.
7. Luo M., Ding L., and Perkel D.J.. An avian basal ganglia pathway essential forvocal learning nucleus in the zebra finch song system forms closed topographic loops. J Neurosci. 2001; 21:6836-45.
8. Luo, M., and Perkel, D.J. (1999) A GABAergic, strongly inhibitory projection to a thalamic nucleus in the zebra finch song system. J Neurosci. 19(15):6700-11.
9. Luo, M., and Perkel, D.J. (1999) Long-range GABAergic projection in a circuit essential for vocal learning. J Comp Neurol 403: 68-84.
相關(guān)報(bào)道：
人嗅覺神經(jīng)元的再生
果蠅的逃避是由一群嗅覺神經(jīng)元決定的
《Science》：嗅覺神經(jīng)元克隆小鼠問世
科學(xué)家揭示為什么一個嗅覺神經(jīng)元只有一個受體
嗅覺神經(jīng)元的發(fā)育
