Analysis of involvement of synaptic plasticity in photoperiodism

2022 Fiscal Year Final Research Report

• Project/Area Number: 20K06739
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Review Section: Basic Section 44050:Animal physiological chemistry, physiology and behavioral biology-related
• Research Institution: Osaka University
• Principal Investigator: Hamanaka Yoshitaka 大阪大学, 大学院理学研究科, 助教 (10647572)
• Project Period (FY): 2020-04-01 – 2023-03-31
• Keywords: 光周性 / 軟体動物 / Caudo-dorsal cell / RNA sequencing

Outline of Final Research Achievements

The pond snail Lymnaea stagnails displays clear photoperiodism in egg-laying behavior, which is known to be triggered by caudo-dorsal cells (CDCs) expressing an ovulation hormone, i.e. CDC hormone (CDCH). We have demonstrated that excitability of CDCs is modulated by photoperiod, which the snails underwent in a previous study. However, the mechanism remains to be revealed. In the present study, I analyzed neurotransmitter receptors that express in CDCs by means of single-cell RNA sequencing, and then I found that plural receptors for a small molecule of classic neurotransmitters express in CDCs. These facts imply that CDCs receive synaptic inputs from unknown pre-synaptic neurons. Accordingly, photoperiod-dependent switching of the excitability of CDCs might be attributed to synaptic plasticity between CDCs and the presynaptic neurons; the latter possibly carrying photoperiodic information to CDCs.

Free Research Field

Neuroethology

Academic Significance and Societal Importance of the Research Achievements

光周期（季節）の情報は脳内の光周時計で処理されると考えられるが, 無脊椎動物の光周時計の正体やその機能原理は未だ不明である。光周性の神経機構にシナプス可塑性が関与するのか？これは未開拓の課題であり, 本研究の学術的意義は高い。本研究により, ヨーロッパモノアラガイの光周期依存的な産卵調節に関わるCDCがシナプスを介した入力を受けることが支持された。季節という長い時間軸を持った情報が脳でどのように処理されるのか？本研究は, 光による環境周期への生物の適応機構を生理学的に解明しようとする試みであり, 神経行動学の面白さを若い世代に広めるという社会的意義も含んでいる。