一般口演
嗅覚と味覚 / その他
Olfaction and Taste / Others
座長：今井 猛（九州大学大学院医学研究院疾患情報研究分野） |
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| 2022年7月3日 11:00～11:15 沖縄コンベンションセンター 会議場A2 第7会場
4O07a1-01
匂いの混合物に対する嗅覚受容体の相乗的応答は正のアロステリック効果によって説明できる
Allosteric modulations in odor mixture responses
*深田 幸平(1)、稲垣 成矩(1)、今井 猛(1)
1. 九州大学大学院医学研究院 生体情報科学講座 疾患情報研究分野
*Kohei Fukata(1), Shigenori Inagaki(1), Takeshi Imai(1)
1. Department of Developmental Neurophysiology, Kyushu University Graduate School of Medical Sciences
Keyword: Olfactory receptor, Olfactory sensory neuron, Allosteric modulation
Sensory signals from the environment are mostly comprised of multiple stimuli. For example, natural odors are comprised of multiple kinds of odorants. Odorants are bound to and activate odorant receptors (ORs) which are expressed by olfactory sensory neurons (OSNs). Each OSN can detect multiple odorants with one type of OR. However, OSN responses to odor mixtures are not necessarily the sum of their responses to the components. OSN responses are often modulated by antagonism and synergy. Previous studies revealed the mechanism of antagonism that occurs at the level of ORs. However, the mechanisms underlying synergy responses remained unclear. Here, we examined a hypothesis that an odorant could act as an allosteric modulator to another odorant. We evaluated the responses of OSNs to odorants using in vivo calcium imaging in the olfactory epithelium. Mice were stimulated with amyl acetate (Aa), three consecutive linear aliphatic aldehydes (ALD), and mixtures of Aa with each ALD. First, we compared the responses of OSNs to three different concentrations of Aa and their mixtures with an ALD, pentanal. For some OSNs that didn’t respond to pentanal, we observed a synergistic response to the mixture. In addition, there was a leftward shift in the dose-response curve, indicating an allosteric response enhancement. Allosteric modulation was found for specific aldehydes, suggesting ligand specificity. Thus, specific binding of an allosteric modulator odorant can positively regulate OR responses to agonist odorants. | | 2022年7月3日 11:15～11:30 沖縄コンベンションセンター 会議場A2 第7会場
4O07a1-02
ショウジョウバエ二次嗅覚中枢における生得的な匂い価値の神経表現
Representation of innate odor value in the secondary olfactory center of Drosophila
*染谷 真琴(1)、風間 北斗(1,2)
1. 理化学研究所 脳神経科学研究センター、2. 東京大学大学院 総合文化研究科
*Makoto Someya(1), Hokto Kazama(1,2)
1. RIKEN Center for Brain Science, Saitama, Japan, 2. Grad Sch Arts and Sci, Univ of Tokyo, Tokyo, Japan
Keyword: Olfactory processing, Drosophila, Value coding, Calcium imaging
Odors are intrinsically associated with values as they induce innate behaviors such as attraction and aversion. However, how innate values of odors are represented in the brain remains unclear. We are addressing this question using the olfactory circuit of fruit fly Drosophila. In Drosophila, olfactory information processed in the primary olfactory center, the antennal lobe (AL), is transmitted to two secondary olfactory centers; the mushroom body (MB) involved in associative learning and the lateral horn (LH) implicated in innate olfactory behavior. As opposed to MB neurons, the physiology of LH neurons has received little investigation because of a lack of tools to specifically and comprehensively label these neurons. Here we developed an optogenetic technique and an image analysis pipeline to track virtually all the neurons in the LH and examined their computation using volumetric calcium imaging. We found that the LH encodes innate odor value more accurately than the MB. Subsets of LH neurons were tuned to either positive or negative odor values and were spatially clustered. Using the electron microscopy derived synaptic connectivity between neurons in the AL and the LH, we were able to reproduce the odor responses of LH neurons encoding the negative but not positive values from the activity of AL output neurons. This suggests that the representation of negative odor value emerges through integration of feedforward input whereas that of positive odor value emerges through additional local interactions within the LH. During the presentation, we will further discuss the computations and mechanisms operating in the LH. | | 2022年7月3日 11:30～11:45 沖縄コンベンションセンター 会議場A2 第7会場
4O07a1-03
逃避行動における行動スイッチングの神経基盤
Neuronal mechanisms underlying behavioral switching during nociceptive escape
*中溝ー堂上 真未(1)、石井 健一(1)、榎本 和生(1)
1. 東京大学理学系研究科生物科学専攻脳機能学分野
*Mami Dojo Nakamizo(1), Kenichi Ishii(1), Kazuo Emoto(1)
1. Department of Biological Sciences, Graduate School of Science, The University of Tokyo, Tokyo, Japan
Keyword: Escape behavior, Nociception, Behavioral transition, GABA
Escaping from noxious stimuli is critical for animal survival. Such nociceptive escape involves a coordinated series of initiation/termination of distinct behaviors, which is achieved by complex interplay of excitatory/inhibitory neural circuitry. In Drosophila larvae, the initiation of nociceptive escape is triggered by class IV da (C4da) neurons that sense various types of noxious stimuli. Activation of C4da and their downstream neurons leads to stereotyped “rolling” that ends within a few seconds, followed by a sharp switch to high-speed forward crawling. Among those C4da downstream targets, several subtypes of second-order neurons involved in rolling initiation have been successfully mapped by us (Yoshino, et al. 2017) and other groups (Ohyama, et al. 2015; Hu, et al. 2017). However, the neurogenetic mechanism that terminates rolling and hence allows the behavioral transition for efficient escape remains unknown.
To address this issue, we first performed a behavioral screen for interneurons that suppress larval rolling triggered via forced activation of C4da. This revealed a specific subset of inhibitory neurons in the brain, herein designated as “M” neurons, with descending axons that directly innervate onto C4da axonal terminals. Silencing of M neurons increased both sensitivity and duration of the rolling behavior upon noxious stimuli. Conversely, acute activation of M neurons by optogenetic stimulation immediately arrested larval rolling, even in the presence of potent C4da stimulants. We next asked how C4da and M neurons communicate with each other during the nociceptive responses. Calcium imaging demonstrated that M neurons were activated following optogenetic stimulation of C4da neurons, and interestingly vice versa. Further physiological and behavioral analyses suggested that activated M neurons sent GABAergic inhibitory inputs to C4da, which led to rolling termination. Taken together, we propose for the first time a feedback neural circuit which controls the behavior switching during nociceptive escape in Drosophila larvae. Our findings provide a simple model to understand the crosstalk between peripheral and central nervous systems that regulate nociceptive responses. Noteworthy, escape behaviors are affected by the animals’ internal states such as blood sugar and hormone level changes. | | 2022年7月3日 11:45～12:00 沖縄コンベンションセンター 会議場A2 第7会場
4O07a1-04
頭部固定下マウスによる新規到達把持運動課題の開発
A new reaching, grasping, and retrieving task device for mice under head fixation
*真仁田 聡(1)、池添 貢司(1)、喜多村 和郎(1)
1. 山梨大学
*Satoshi Manita(1), Koji Ikezoe(1), Kazuo Kitamura(1)
1. University of Yamanashi
Keyword: forelimb movements, behavioral task, water restriction, agar cube
Rodents frequently perform reaching, grasping, and retrieving movements in their daily lives. To investigate how single neuronal activities are involved in these movements, it is necessary to measure or control their activities during these behaviors. For stable electrophysiological or optical recordings of neural activity in a behaving animal, head fixation is effective in minimizing motion artifacts. In this study, we present a new method for investigating the neural mechanisms involved in the reaching, grasping, and retrieving behavior of head-fixed mice. We developed a new behavioral experimental system in which head-fixed mice could grasp an agar cube using their forelimb. An agar dispenser for making agar cubes consists of an agar mold, two plungers, and a control unit. Agar solution was poured into the mold and hardened, and the hardened agar was extruded from the agar mold using two orthogonal plungers to form a cube. The movements of the plungers were controlled by independent, self-made linear actuators. A microcontroller (Arduino Uno Rev3) and a motor drive shield attached to the Arduino were used to control the movements of the two motors used in the actuators. Reaching, grasping, and retrieving movements of the mouse were recorded at a 100 Hz frame rate with an infrared LED illumination using two USB3 cameras. We examined the reproducibility of the agar cubes produced by the device and showed that the size of agar cubes created by the dispenser was consistent each time, and each agar cube could be presented in position with an accuracy of less than 1 mm. We also showed that the mice performed the task with mild water restriction (less than 20% body weight loss) Moreover, we found that placing the agar cube farther away made the task more difficult, and repeating the task increased the success rate. Our system can be used to unveil the relationship between neural activity and reaching movements and underlying neural circuit mechanisms. | |
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