嗅覚、味覚、化学感覚 Olfaction, Taste, Chemical Senses
P3-2-25 ショウジョウバエ幼虫の走化性行動時における新規行動様式の同定と機能解析 Continuous biased running during chemotaxis of Drosophila larvae ○森本高子1, 大橋春平2, 宮川博義1, 青西享2 ○Takako Morimoto1, Shumpei Oohashi2, Hiroyoshi Miyakawa1, Toru Aonishi2 東京薬科大学生命科学部1, 東京工業大学総合理工学研究科2 Dept. Neurobiol. Tokyo Univ. of Pharm and Life Sci.1, Int. Grad. Sch. of Sci. and Eng., Tokyo Tech2 Chemotaxis is the phenomenon in which animals orient toward or against the target in response to chemical gradients of attractants or repellents. In C. elegans, they use two behavioral strategies named pirouette and weathervane during chemotaxis. In Drosophila larvae, sharp turns corresponding to the pirouette have been focused as a main strategy during locomotion to odorant sources, but the existence of successive slow orientations, which correspond to the weathervane, has not been described. On the other hand, most animals including Drosophila larvae have bilateral olfactory organs and it has been proposed that they compare and process the signals from these organs to detect the direction of the stronger signal. However, ones which were disrupted one of two organs can orient to the correct direction although the efficiency is lowered. Therefore, it is still controversial that animals truly use the differences in odor concentration between bilateral organs to find out the odor source. Here, we investigated the behavioral strategy of Drosophila larvae during chemotaxis toward an attracting food source. First, we found the successive slow orientation, which we named 'biased running', in wild type (WT) by analyzing the relation between the rotational velocities to larval moving directions and larval positions relative to a food source. Next, we studied behaviors of genetically manipulated larvae which have unilateral or bilateral functional olfactory organs (U-larvae or B-larvae). Interestingly, WT and B-larvae, but not U-larvae, showed the biased running. Moreover, only in WT and B-larvae, concentration gradients of chemoattractants between left and right olfactory organs, which were theoretically estimated, were statistically correlated with rotational velocities during the biased running. These results suggest that the stereo information provided from bilateral olfaction is important cue for the newly found behavioral strategy, biased running.	P3-2-26 徐波睡眠時における嗅皮質および前頭眼窩皮質の協調的活動 Coordinated activity of anterior piriform cortex and orbitofrontal cortex during slow-wave sleep ○鬼沢菜穂美1,2, 眞部寛之1,2, 森憲作1,2 ○Naomi Onisawa1,2, Hiroyuki Manabe1,2, Kensaku Mori1,2 東京大院・医・細胞分子生理1 Dept Physiol, Univ of Tokyo, Tokyo, Japan1, JST CREST2 Olfactory cortex (OC) shows highly synchronized discharges that accompany with sharp-waves (OC-SPWs) during slow-wave sleep. The highly synchronized discharges of OC neurons are thought to be involved in the reorganization of the central neuronal circuits of the olfactory system. Because orbitofrontal cortex (OFC) has massive reciprocal connections with OC, we examined whether the generation of OC-SPWs correlates with slow-wave activity of OFC during slow-wave sleep. We made multi-units and local field potential recordings with tetrodes simultaneously from OC and OFC in freely behaving rats. Local field potentials in the OFC showed slow oscillations consisting of long-lasting up-state and down-state. Many OC-SPWs occurred just after the transition from down-state to up-state of OFC local field potential. Furthermore, some OFC neurons showed spike discharges in synchrony with OC-SPWs. These results indicate that generation of highly synchronized discharges in the OC is coordinated with that of slow-wave activity in the OFC.
P3-2-27 ドレブリンノックアウトマウスに見られる嗅覚異常 Drebrin knockout mice show the impairment of olfactory acuity ○梶田裕貴1, 児島伸彦1, 崎村建司2, 白尾智明1 ○Yuki Kajita1, Nobuhiko Kojima1, Kenji Sakimura2, Tomoaki Shirao1 群馬大学院　医学系研究科　神経薬理学1, 新潟大　脳研　細胞神経生物学2 Gunma Univ., Grad.Sch. of Med., Dept of Neurobiol. Behav., Maebashi, Japan1, Dept. Cell. Neurobiol., Brain Res. Inst., Niigata, Japan2 Drebrin is an F-actin-binding protein and consists of two major isoforms, drebrin A and E. Drebrin A is a neuron-specific protein, and its physiological role is well studied using drebrin-A-specific knockout mouse. On the other hand, drebrin E is widely distributed in some non-neuronal cells as well as neurons, and the physiological role of drebrin E is not fully clarified. To better understand the role of drebrin E in the brain function, we generated drebrin knockout mice (DXKO). We subjected adult male DXKO to a battery of general behavioral tests and olfaction acuity test to explore the functional role of drebrin. Olfaction acuity test was examined by measuring the time that mice spend to discover a piece of food buried in the litter of the cage. We also immunohistochemically analyzed the number of mature and newly generated neurons involved in the olfaction. DXKO did not show any gross morphological abnormality. However, they showed significantly longer latency to locate the buried food than wild type mice (WT), although they did not show any differences in other general behavioral profiles. In addition, the number of doublecortin-immunopositive immature neurons in the rostral migratory stream was significantly decreased to about 70% of that of WT. In contrast, the number of NeuN-positive mature neurons in the olfactory bulb (OB) of DXKO was not decreased. The present behavior analysis indicated that DXKO show impairment of olfaction. Because immature neurons in the rostral migratory stream are generated in the subventricular zone of lateral ventricle in adult mouse brain, the immunohistochemical data indicate that the adult neurogenesis in DXKO is reduced. Although at present we cannot determine the causal relationship between the reduction of adult neurogenesis and olfactory deficit, DXKO mice may serve as an animal model for olfactory disorders with the impairment of neurogenesis in the adult OB.	P3-2-28 嗅覚可塑性を制御する神経ペプチド遺伝子snet-1の発現がフェロモンによって調節される機構の解析 Analysis of the pheromone signaling in C. elegans that regulates olfactory plasticity through changing the expression of the neuropeptide gene snet-1 ○鳥谷部啓1, 山田康嗣1,2, 澤村佳之1, 飯野雄一1 ○Hiroshi Toriyabe1, Koji Yamada1,2, Yoshiyuki Sawamura1, Yuichi Iino1 東京大院・理・生物化学1, 理研・BRC・細胞材料2 Dept. of Biophy. and Biochem., Grad.Sch. of Sci., Univ. of Tokyo, Tokyo1, RIKEN, BRC, CED, Japan2 Pheromones of C. elegans were recently identified as mixtures of sugar derivatives called ascarosides. Ascaroside signaling regulates various behaviors, such as sex-specific attraction, repulsion, dauer formation, aggregation and olfactory plasticity. However, the molecular mechanisms of pheromonal signaling, especially regulation of olfactory plasticity, remain elusive. Olfactory plasticity is also regulated by pheromones. C. elegans is attracted to a series of odorants. However, after prolonged exposure to the odor in the absence of food, worms stop approaching the odorant and disperse from it. We recently reported that abundant pheromone is required for olfactory plasticity. Low concentration of pheromone results in an over-production of a neuropeptide SNET-1 which in turn inhibits the olfactory plasticity. snet-1 is expressed in a subset of head neurons, including the pheromone-sensing neurons ASI, in which expression of snet-1 was observed only in the absence of pheromone. By observing the expression of snet-1p::venus in ASI neurons of mutant animals, we found that known pheromone signaling molecules are also involved in its regulation: cGMP/CNG channel pathway and insulin pathway promote snet-1 expression, and TGF-β pathway represses the expression. To identify novel genes that relay pheromonal signals, we mutagenized snet-1p::venus animals by ethyl methanesulfonate (EMS) and screened for mutants that showed constitutive expression of Venus reporter in ASI neurons. In the screen, we obtained six candidate genes. snet-1 expression was not detected in olfactory neurons. In the plasticity regulation, pheromone-sensing neurons may modulate the response of olfactory sensory neurons through changing snet-1 expression in pheromone-sensing neurons.
P3-2-29 C. elegans 温度受容ニューロンにおけるGタンパク共役型受容体による温度受容の制御 Regulation of thermosensation by SRTX-1 (GPCR) in AFD thermosensory neurons in C. elegans ○笹倉寛之1,2, 伊藤浩子1, 小林曉吾1, 鈴木啓太1, 森郁恵1,2 ○Hiroyuki Sasakura1,2, Hiroko Ito1, Kyogo Kobayashi1, Keita Suzuki1, Ikue Mori1,2 名古屋大学大学院 理学研究科 生命科学専攻 分子神経生物学1, CREST, 科学技術振興機構2 Group of Molecular Neurobiology, Division of Biological Science, Graduate School of Science, Nagoya University1, CREST, JST, Japan2 Temperature is a ubiquitous stimulus that affects our life. Although TRP ion channels are known to detect a wide range of temperatures, molecular basis for thermosensation is still largely unknown. C. eleganssenses the environmental temperature by two pairs of sensory neurons, AFD and AWC. Signal transduction pathway for temperature in AFD and AWC is similar to that in visual and olfactory system in mammals (Mori et al., 2007; Kuhara et al., 2008). A recent study showed that Rhodopsin, a G protein-coupled receptor (GPCR), function in temperature discrimination in Drosophila larva (Shen et al., 2011). It is thus plausible to hypothesize that GPCRs play an important role for sensing the environmental temperature. Previous reports showed that srtx-1 encodes the GPCR specifically expressed in AFD and AWC (Colosimo et al., 2004; Biron et al., 2008). C. elegans exhibits thermotaxis; on a temperature gradient, wild type animals migrated to the temperature that corresponds to the previous cultivation temperature (Hedgecock and Russell 1975). srtx-1 mutants migrated to colder temperature after cultivated at high temperature such as 23 or 20 degree, and migrated to warmer temperature after cultivated at low temperature such as 17 degree. It is likely that SRTX-1 is required for sensing a wide range of temperatures. The expression of srtx-1cDNA only in AFD restored these defects. Calcium imaging revealed that AFD response to temperature is decreased in srtx-1 mutants. The overexpression of srtx-1cDNA in AFD of wild type severely altered thermotaxis. A part of the animals overexpressing srtx-1 showed thermophilic phenotype and this phenotype was suppressed by the loss of themosensory signaling in AFD, which implicates the role of SRTX-1 upstream of thermosensory signaling pathway. We propose that SRTX-1 (GPCR) is a key component for thermosensation in AFD through regulating temperature sensing range.	P3-2-30 ヘパラン硫酸エンドスルファターゼSulf1の嗅覚記憶における役割 Roles of heparan sulfate endosulfatase Sulf1 in olfactory learning in mouse ○桝和子1, 奥谷文乃2, 椛秀人2, 桝正幸1 ○Kazuko Keino-Masu1, Fumino Okutani2, Hideto Kaba2, Masayuki Masu1 筑波大学　医学医療系　分子神経生物学1, 高知大学　医学部2 Dept Mol Neurobiol, Unv of Tsukuba, Tsukuba1, Dept Physiol, Kochi Med Univ2 Heparan sulfate (HS) plays important roles in cell growth, differentiation, axon guidance, synaptogenesis, and synaptic functions in the nervous system. HS is a linear carbohydrate chain composed of repeating disaccharides each composed of glucuronic acid or iduronic acid and glucosamine. HS interacts with a wide variety of signaling molecules, including growth factors, cytokines, axon guidance molecules, receptors, and extracellular matrix molecules. The interaction is mainly mediated by sulfate residues in the HS chain. Previous biochemical studies have shown that sulfation patterns in the sugar chain are an important factor for determining specificity and affinity of the interaction between HS and binding molecules. Extracellular sulfatases, Sulf1 and Sulf2, specifically remove 6-O-sulfate in the glucosamine residues in highly-sulfated domains of HS. 6-O-desulfation by Sulf1 or Sulf2 activates Wnt pathway and suppress growth factor signaling. Sulf1 is highly expressed in the olfactory system, including the olfactory bulb, olfactory tubercle, piriform cortex, and entorhinal cortex in the adult mouse brain. We thus attempted to elucidate the possible roles of Sulf1 gene in the olfactory function by testing olfactory learning in Sulf1 knockout mice. Neonatal mice were repeatedly conditioned by simultaneous presentation of an odor and electrical shock. Next day odor preference was tested by measuring the time spent over the odor area against a neutral odor. Subsequently, we examined the neuronal activity during olfactory learning by c-fos immunohistochemistry. We found that c-fos-positive cells were present in the mitral cell layer and granule cell layer of the olfactory bulb, olfactory cortices, hippocampus, and some hypothalamic nuclei. Finally, we compared the intensity of c-fos staining between the wild-type and Sulf1 knockout mice.
P3-2-31 マウス嗅覚によるCO2感知機構の解析 Molecular basis of CO2 sensing in the mouse olfactory system ○高橋弘雄1, 吉原誠一1, 玉田喜規1, 廣野順三2, 佐藤孝明2, 坪井昭夫1 ○Hiroo Takahashi1, Sei-ichi Yoshihara1, Yoshinori Tamada1, Junzo Hirono2, Takaaki Sato2, Akio Tsuboi1 奈良医大・先端研・脳神経システム1, 産総研・細胞分子機能2 Lab for Mol Biol of Neural System, Nara Med Univ, Kashihara1, Funct Biomol Res Gr, Health Res Inst, AIST, Amagasaki2 Carbon dioxide (CO2) is an important environmental cue for many organisms. In mammal, mouse, rat and guinea pig have a CO2 sensor in the olfactory epithelium (OE). Mice can detect CO2 at concentrations around the average atmospheric level by olfaction. In the ventro-lateral region of the mouse OE, there is a unique subset of olfactory sensory neurons (OSNs), termed GC-D OSNs, which express carbonic anhydrase 2 (Car2) and guanylate cyclase-D (GC-D), instead of odorant receptor. In GC-D neurons, Car2 and GC-D function as a sensor for CO2, urinary peptides and carbon disulfide (CS2) that mediates food-related social learning. Here, we report that at least two novel subsets of OSNs, which are not expressing Car2, respond to CO2 as well. In contrast to GC-D OSNs, these CO2-responding neurons did not react to both urinary peptides and CS2. Interestingly, acidic pH solution activated only about half of Car2(-)-CO2 sensor cells. This means that Car2(-)-CO2 sensing OSNs can be divided into two types: the one is CO2-sensing; the other acidic pH sensing. Treatment of a carbonic anhydrase inhibitor, acetazolamide, suppressed the response to CO2 in CO2-sensing OSNs. Among 16 genes encoding the carbonic anhydrase family, we have found that carbonic anhydrase 7 (Car7) is expressed in a subset of OSNs, instead of Car2. Similar observation was done in the vomeronasal epithelium (VNE). These results suggest that mice sense CO2 not only with GC-D OSNs, but also with novel subsets of sensory neurons in the OE and VNE.	P3-2-32 ラット大脳味覚野の左右非対称性 Asymmetrical gustatory cortex in both hemispheres of the rodent brain ○黄田育宏1, 圓見純一郎2, 星詳子3, 根本正史3, 飯田秀博2, 井口義信3, 吉岡芳親4 ○Ikuhiro Kida1, Jun-ichiro Enmi2, Yoko Hoshi3, Masahito Nemoto3, Hidehiro Iida2, Yoshinobu Iguchi3, Yoshichika Yoshioka4 情報通信研究機構・脳情報通信融合研究センター・計測基盤グループ1, 国立循環器病研究センター研究所・画像診断医学部2, 東京都医学総合研究所・ヒト統合脳機能プロジェクト3, 阪大・免疫学フロンティア研究センター4 CiNet, NICT, Osaka1, Dept Investigative Radiology, National Cerebral and Cardiovascular Center Research Institute, Osaka2, Integrated Neurosci Res Project, Tokyo Metropolitan Institute of Medical Science, Tokyo3, iFReC, Osaka University, Osaka4 While anatomical and functional asymmetries are well known in the human brain, asymmetrical processing of brain function is not fully understood in rodents. Our previous study using blood oxygenation level dependent functional magnetic resonance imaging demonstrated that tastants evoke bilateral responses in the insular cortices, but that these representations are asymmetrical in rodents. Two interpretations may explain this asymmetry. First, this region may contain asymmetrical functional representations with respect to anatomical boundaries. Alternatively, the representations may be symmetric, but have asymmetric anatomical landmarks, which has been identified near the anterior and posterior regions of the middle cerebral artery (mca) and the dorsal regions of the rhinal vein (rv) in the insular cortex of rodents. We performed optical imaging of intrinsic signals to measure the functional representations elicited by tastant solutions. We also used magnetic resonance angiography (MRA) at 7.0 Tesla to observe the landmark coordinates within the insular cortices of both hemispheres. The sucrose solution increased the CBV in the anterior and posterior areas of the mca and the dorsal regions of the rv in the insular cortices of both hemispheres. The averaged changes in CBV were not statistically significant between the anterior and posterior regions in both hemispheres, which indicates a symmetrical functional response with respect to the mca in both hemispheres. MRA indicated that the landmark location in each hemisphere was asymmetrical. We found that a functional gustatory representation was symmetrically preserved in both hemispheres based on the landmark, but the position of the landmark was asymmetrical between the hemispheres in rodents. This suggests that the cerebral vasculature provides a reliable reference point for functional representations in the gustatory cortex.
P3-2-33 Towards understanding the neuronal basis of olfactory perception in the Drosophila antennal lobe ○Laurent Badel1, Kazumi Ohta1, Yoshiko Tsuchimoto1, Hokto Kazama1 Laboratory for Circuit Mechanisms of Sensory Perception, RIKEN Brain Science Institute, Wako, Japan1 In the insect olfactory system, as in vertebrates, only two synapses separate the sensory periphery from the brain regions involved in memory formation and behavior. Olfactory information received by peripheral receptors transits through the antennal lobe, which then projects to higher-order brain regions such as the mushroom body or the lateral horn. Neurons of interest in these brain regions can be genetically labeled with GFP and their activity can be probed or manipulated using electrophysiological (patch-clamp) or optogenetic methods (e.g., GCaMP or channelrhodopsin). Because the totality of olfactory information transits through the projection neurons (PNs) of the antennal lobe, it is likely that the perception of odors is formed based on the activity of these cells. How this is achieved by the brain, however, is still poorly understood. The goal of this project is to gain a better understanding of how the representation of odors by PNs is linked with odor perception, using a combination of in-vivo physiology, optogenetics and behavior. Flies are placed in a setup in which they are free to fly and perform a range of behavioral responses, while neuronal activity can be simultaneously monitored using electrophysiological and/or imaging techniques. Odor perception is assessed using a two-alternative forced choice task, in which the fly must choose between two different odorant mixtures. Consistent choice behavior can be ensured by choosing combinations of naturally attractive/aversive odors, or by inducing aversion/attraction by means of associative conditioning. The relationship between PN activity and behavior can then be examined by gradually changing the identity of the odors, or by directly activating or inhibiting of a subset of PNs during the task and assessing the impact on the fly's behavior. This presentation reports our recent progress towards achieving this goal.

上部に戻る

前に戻る