2020 Fiscal Year Final Research Report

Green impulse: neuronal network in fish brain driven by green light

Research Project

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Project/Area Number	19K22340
Research Category	Grant-in-Aid for Challenging Research (Exploratory)
Allocation Type	Multi-year Fund
Review Section	Medium-sized Section 40:Forestry and forest products science, applied aquatic science, and related fields
Research Institution	Kitasato University
Principal Investigator	Takahashi Akiyoshi 北里大学, 海洋生命科学部, 教授 (10183849)
Co-Investigator(Kenkyū-buntansha)	阿見彌典子北里大学, 海洋生命科学部, 講師 (20588503) 清水大輔国立研究開発法人水産研究・教育機構, 水研機構(塩釜), グループ長 (40443361) 水澤寛太北里大学, 海洋生命科学部, 准教授 (70458743)
Project Period (FY)	2019-06-28 – 2021-03-31
Keywords	カレイ / 緑色光 / 成長 / 食欲 / 神経ペプチド / メラニン凝集ホルモン
Outline of Final Research Achievements	In the present study, we aimed to identify the neuron network related to somatic growth facilitated by green light irradiation. We found that feeding in spotted halibut was reduced upon the administration of melanin-concentrating hormone (MCH) into the cerebrospinal fluid via an aperture made on the head. The results of this study discredited a hypothesis considering MCH as an appetite-inducing peptide hormone. MCH administration suppressed the expression levels of genes encoding agouti-related protein-1 (AGRP-1) and neuropeptide Y (NPY), which were known as appetite inducers, in the brain of fish. These results suggest that the neuron networks corresponding to MCH, AGRP1, and NPY may regulate the appetite and feeding behavior in fish. Furthermore, they suggest the existence of a functional neuron network comprising these three hormonal neurons. Since MCH may not stimulate the feeding behavior, it is necessary to identify other hormonal factors and neurons instead of just the hormone.
Free Research Field	水圏生命科学
Academic Significance and Societal Importance of the Research Achievements	ホシガレイの摂餌量と成長は緑色光照射よって促進される。この飼育条件下でメラニン凝集ホルモン（MCH）遺伝子の脳内での発現量が上昇すること，また哺乳類ではMCHが食欲を亢進することにもとづいて，MCHを緑色光－脳内作用（食欲亢進）－成長をつなぐインターフェースとして想定してきた。しかし本研究において示された可能性は，従来とは真逆の食欲抑制作用である。これはキンギョで示されている作用と同様である。よって，MCH以外のホルモンをインターフェースに設定して，研究計画を再構築する必要が生じた。