Mabuchi Ikumi, Shimada Naoto, Sato Shoma, Ienaga Kahori, Inami Show, Sakai Takaomi
Department of Biological Sciences, Tokyo Metropolitan University, 1-1 Minamiosawa, Hachioji-shi, Tokyo 192-0397, Japan.
Department of Biological Sciences, Tokyo Metropolitan University, 1-1 Minamiosawa, Hachioji-shi, Tokyo 192-0397, Japan.
Neurosci Res. 2016 Oct;111:25-33. doi: 10.1016/j.neures.2016.04.005. Epub 2016 Apr 19.
In the fruitfly Drosophila melanogaster, circadian rhythms of locomotor activity under constant darkness are controlled by pacemaker neurons. To understand how behavioral rhythmicity is generated by the nervous system, it is essential to identify the output circuits from the pacemaker neurons. A recent study of Drosophila has suggested that pacemaker neurons project to mushroom body (MB) neurons, which are considered the memory center in Drosophila. MBs also regulate spontaneous locomotor activity without learning, suggesting that MB neuronal activity regulates behavioral rhythms. However, the importance of MBs in generating behavioral rhythmicity remains controversial because contradicting results have been reported as follows: (1) locomotor activity in MB-ablated flies is substantially rhythmic, but (2) activation of restricted neuronal populations including MB neurons induces arrhythmic locomotor activity. Here, we report that neurotransmission in MBs is required for behavioral rhythmicity. For adult-specific disruption of neurotransmission in MBs, we used the GAL80/GAL4/UAS ternary gene expression system in combination with the temperature-sensitive dynamin mutation shibire(ts1). Blocking of neurotransmission in GAL4-positive neurons including MB neurons induced arrhythmic locomotor activity, whereas this arrhythmicity was rescued by the MB-specific expression of GAL80. Our results indicate that MB signaling plays a key role in locomotor activity rhythms in Drosophila.
在果蝇黑腹果蝇中，恒定黑暗条件下运动活动的昼夜节律由起搏器神经元控制。为了理解神经系统如何产生行为节律，确定起搏器神经元的输出回路至关重要。最近一项对果蝇的研究表明，起搏器神经元投射到蘑菇体（MB）神经元，蘑菇体被认为是果蝇的记忆中心。蘑菇体在没有学习的情况下也调节自发运动活动，这表明蘑菇体神经元活动调节行为节律。然而，蘑菇体在产生行为节律中的重要性仍存在争议，因为有如下相互矛盾的结果报道：（1）蘑菇体切除的果蝇的运动活动具有显著的节律性，但（2）包括蘑菇体神经元在内的特定神经元群体的激活会诱导无节律的运动活动。在此，我们报告蘑菇体中的神经传递是行为节律所必需的。为了在成年果蝇中特异性破坏蘑菇体中的神经传递，我们将GAL80/GAL4/UAS三元基因表达系统与温度敏感的发动蛋白突变体失活（ts1）结合使用。阻断包括蘑菇体神经元在内的GAL4阳性神经元中的神经传递会诱导无节律的运动活动，而这种无节律性可通过蘑菇体特异性表达GAL80得到挽救。我们的结果表明，蘑菇体信号在果蝇的运动活动节律中起关键作用。
