{"created":"2021-03-01T06:22:19.895040+00:00","id":5629,"links":{},"metadata":{"_buckets":{"deposit":"a00a22f0-6bdd-4b68-9861-7478cf583d13"},"_deposit":{"id":"5629","owners":[],"pid":{"revision_id":0,"type":"depid","value":"5629"},"status":"published"},"_oai":{"id":"oai:repository.dl.itc.u-tokyo.ac.jp:00005629","sets":["75:275:400","9:233:280"]},"item_7_alternative_title_1":{"attribute_name":"その他のタイトル","attribute_value_mlt":[{"subitem_alternative_title":"線虫C. elegansの化学感覚を制御する神経回路"}]},"item_7_biblio_info_7":{"attribute_name":"書誌情報","attribute_value_mlt":[{"bibliographicIssueDates":{"bibliographicIssueDate":"2013-03-25","bibliographicIssueDateType":"Issued"},"bibliographic_titles":[{}]}]},"item_7_date_granted_25":{"attribute_name":"学位授与年月日","attribute_value_mlt":[{"subitem_dategranted":"2013-03-25"}]},"item_7_degree_grantor_23":{"attribute_name":"学位授与機関","attribute_value_mlt":[{"subitem_degreegrantor":[{"subitem_degreegrantor_name":"University of Tokyo (東京大学)"}]}]},"item_7_degree_name_20":{"attribute_name":"学位名","attribute_value_mlt":[{"subitem_degreename":"博士(理学)"}]},"item_7_description_5":{"attribute_name":"抄録","attribute_value_mlt":[{"subitem_description":"動物は外界からの刺激を感覚神経で受容し、その情報を神経回路上で処理することにより、刺激に対して適切な応答を行っている。例えば、線虫はNaClを味覚神経ASEで受容し、介在神経を含む神経回路を介してシグナルを伝達し、誘引行動を引き起こす。線虫のNaClへの誘引行動はピルエット機構と風見鶏機構という2つの機構により達成されていることが知られており、これらの機構には味覚神経ASEと下流の介在神経AIZが関与することが示されている。しかし、これら2つの機構の神経回路基盤の全ては明らかにされていない。本研究では、特定の神経を破壊した線虫の行動を測定し、2つの機構を制御する神経回路の同定を行った。その結果、ピルエット機構にのみ重要な介在神経AIA、AVAと運動神経SMD、風見鶏機構にのみ重要な介在神経AIY、両方の機構に重要な感覚神経ASIと介在神経AIB、運動神経SMBの存在が明らかとなった。これらのことから、NaClへの誘引行動の際に用いられる2つの機構は、部分的に異なる神経回路により制御されていることが示唆される。前述のように、動物は外界からの刺激に対して特定の応答を示すが、その応答は刺激の強度に依存して変化することが知られている。線虫の嗅覚系でも同様に、低濃度で誘引行動を示す匂い物質に対して、高濃度では忌避行動を示す現象が報告されている。しかし、刺激強度に依存した行動変化の神経・分子メカニズムについてはあまりわかっていない。そこで本研究では、線虫の匂いの濃度に依存した行動変化を調節する神経回路・分子メカニズムの解析を行った。匂いに対する誘引行動には、前述の2つの行動戦略が関与していることが知られている。行動解析の結果、そのうちピルエット機構が、匂いの濃度による誘引行動から忌避行動への走性行動の切り替えを主に制御していることがわかった。さらに遺伝学的解析と神経破壊実験により、行動を引き起こすのに関わる感覚神経の組み合わせが匂いの濃度によって異なっており、低濃度と高濃度の匂いに対する行動にはそれぞれ感覚神経AWCとASHが特に重要であることが示された。Ca2+イメージングによって匂いに対する神経応答を測定した結果、AWC神経は低濃度の匂いにのみ応答し、高濃度のときには他の神経からの抑制を受け、匂いには応答しないことが明らかになった。一方、ASH神経は高濃度の匂いにのみ応答を示すことが分かった。これらのことから、匂いの濃度情報が感覚神経における応答の差異を生み出すことで行動が切り替えられていると考えられ、線虫における匂いの濃度情報処理の主要な部分は感覚神経で行われていることが示唆される。","subitem_description_type":"Abstract"},{"subitem_description":"Animals sense various environmental stimuli and process the sensory information by the neural circuits to generate appropriate behavior in response to the stimuli. The model organism C. elegans detects NaCl by ASE gustatory neurons and shows attraction to NaCl. It has been shown that the attraction to NaCl is generated by two behavioral strategies called pirouette and weathervane strategies and that ASE sensory neurons and their downstream interneurons AIZ are required for both of these behavioral responses. However, the rest of the neural circuits underlying these behavioral mechanisms remain largely unknown. Here I observed the behavioral responses of animals with candidate neurons killed. AIA and AVA interneurons and SMD motor neurons are responsible only for the pirouette response, whereas AIY interneurons are required only for the weathervane response. Moreover, AIB interneurons and SMB head motor neurons are responsible for both behavioral responses. These results suggest the existence of partially distinct neural circuits regulating the two behavioral strategies for attraction to NaCl. Although animals show a specific response to each environmental stimulus as mentioned above, response to a particular stimulus can change depending on the strength of the stimulus. However, little is understood about the neural basis of this phenomenon. C. elegans avoids higher concentrations of odorants that are attractive at the lower concentrations. Here I analyzed this odor concentration-dependent change in olfactory preference. Behavioral analyses revealed that the odor concentration-dependent behavior is primarily generated by the pirouette mechanism. Genetic analyses and lesion experiments showed that distinct combinations of sensory neurons function at different concentrations of the odorant; AWC and ASH sensory neurons have critical roles for attraction to or avoidance of the odorant, respectively. Calcium imaging showed that AWC neuron responds to only lower concentrations of the odorant, and their responses disappear at higher concentrations probably due to a suppression effect of synaptic transmission from other neurons. On the other hand, ASH neurons responded to only higher concentrations of odorant. Hence, these results suggest that the odor concentration information in C. elegans is primarily modulated at the sensory neuron level.","subitem_description_type":"Abstract"}]},"item_7_full_name_3":{"attribute_name":"著者別名","attribute_value_mlt":[{"nameIdentifiers":[{"nameIdentifier":"11712","nameIdentifierScheme":"WEKO"}],"names":[{"name":"吉田, 和史"}]}]},"item_7_identifier_registration":{"attribute_name":"ID登録","attribute_value_mlt":[{"subitem_identifier_reg_text":"10.15083/00005620","subitem_identifier_reg_type":"JaLC"}]},"item_7_select_21":{"attribute_name":"学位","attribute_value_mlt":[{"subitem_select_item":"doctoral"}]},"item_7_text_22":{"attribute_name":"学位分野","attribute_value_mlt":[{"subitem_text_value":"Science(Rigaku)(理学)"}]},"item_7_text_24":{"attribute_name":"研究科・専攻","attribute_value_mlt":[{"subitem_text_value":"Department of Earth and Planetary Science, Graduate School of Science (理学系研究科地球惑星科学専攻)"}]},"item_7_text_4":{"attribute_name":"著者所属","attribute_value_mlt":[{"subitem_text_value":"東京大学大学院理学系研究科生物化学専攻"}]},"item_creator":{"attribute_name":"著者","attribute_type":"creator","attribute_value_mlt":[{"creatorNames":[{"creatorName":"Yoshida, Kazushi"}],"nameIdentifiers":[{"nameIdentifier":"11711","nameIdentifierScheme":"WEKO"}]}]},"item_files":{"attribute_name":"ファイル情報","attribute_type":"file","attribute_value_mlt":[{"accessrole":"open_date","date":[{"dateType":"Available","dateValue":"2017-06-01"}],"displaytype":"detail","filename":"Thesis_yoshidakazushi.pdf","filesize":[{"value":"7.7 MB"}],"format":"application/pdf","licensetype":"license_note","mimetype":"application/pdf","url":{"label":"Thesis_yoshidakazushi.pdf","url":"https://repository.dl.itc.u-tokyo.ac.jp/record/5629/files/Thesis_yoshidakazushi.pdf"},"version_id":"dfbff28e-5ed4-4658-84fc-fd079c210400"}]},"item_language":{"attribute_name":"言語","attribute_value_mlt":[{"subitem_language":"eng"}]},"item_resource_type":{"attribute_name":"資源タイプ","attribute_value_mlt":[{"resourcetype":"thesis","resourceuri":"http://purl.org/coar/resource_type/c_46ec"}]},"item_title":"Analysis of neural circuit mechanisms regulating chemical sensation in C. elegans","item_titles":{"attribute_name":"タイトル","attribute_value_mlt":[{"subitem_title":"Analysis of neural circuit mechanisms regulating chemical sensation in C. elegans"}]},"item_type_id":"7","owner":"1","path":["280","400"],"pubdate":{"attribute_name":"公開日","attribute_value":"2014-02-24"},"publish_date":"2014-02-24","publish_status":"0","recid":"5629","relation_version_is_last":true,"title":["Analysis of neural circuit mechanisms regulating chemical sensation in C. elegans"],"weko_creator_id":"1","weko_shared_id":null},"updated":"2022-12-19T03:47:12.567522+00:00"}