Guo Xiaojiao, Ma Zongyuan, Kang Le
State Key Laboratory of Integrated Management of Pest Insects and Rodents, Institute of Zoology, Chinese Academy of Sciences Beijing, China.
Front Behav Neurosci. 2013 Oct 7;7:129. doi: 10.3389/fnbeh.2013.00129. eCollection 2013.
The behavioral plasticity of locusts is a striking trait presented during the reversible phase transition between solitary and gregarious individuals. However, the results of serotonin as a neurotransmitter from the migratory locust Locusta migratoria in phase transition showed an alternative profile compared to the results from the desert locust Schistocerca gregaria. In this study, we investigated the roles of serotonin in the brain during the phase change of the migratory locust. During the isolation of gregarious nymphs, the concentration of serotonin in the brain increased significantly, whereas serotonin receptors (i.e., 5-HT 1 , 5-HT 2 , and 5-HT 7 ) we identified here showed invariable expression patterns. Pharmacological intervention showed that serotonin injection in the brain of gregarious nymphs did not induced the behavioral change toward solitariness, but injection of this chemical in isolated gregarious nymphs accelerated the behavioral change from gregarious to solitary phase. During the crowding of solitary nymphs, the concentration of serotonin in the brain remained unchanged, whereas 5-HT 2 increased after 1 h of crowding and maintained stable expression level thereafter. Activation of serotonin-5-HT2 signaling with a pharmaceutical agonist inhibited the gregariousness of solitary nymphs in crowding treatment. These results indicate that the fluctuations of serotonin content and 5-HT 2 expression are results of locust phase change. Overall, this study demonstrates that serotonin enhances the solitariness of the gregarious locusts. Serotonin may regulate the withdrawal-like behavioral pattern displayed during locust phase change and this mechanism is conserved in different locust species.
蝗虫的行为可塑性是其在独居和群居个体之间可逆相变过程中呈现出的一个显著特征。然而，与沙漠蝗虫沙漠飞蝗（Schistocerca gregaria）相变过程中血清素作为神经递质的研究结果相比，飞蝗Locusta migratoria的研究结果呈现出不同的情况。在本研究中，我们调查了血清素在飞蝗相变过程中在大脑中的作用。在群居若虫隔离期间，大脑中血清素的浓度显著增加，而我们在此鉴定出的血清素受体（即5-HT 1、5-HT 2和5-HT 7）显示出不变的表达模式。药理学干预表明，向群居若虫大脑中注射血清素并未诱导其行为向独居转变，但向隔离的群居若虫注射这种化学物质会加速其行为从群居向独居阶段的转变。在独居若虫拥挤期间，大脑中血清素的浓度保持不变，而5-HT 2在拥挤1小时后增加，此后保持稳定的表达水平。用药物激动剂激活血清素-5-HT2信号通路可抑制独居若虫在拥挤处理中的群居性。这些结果表明，血清素含量和5-HT 2表达的波动是蝗虫相变的结果。总体而言，本研究表明血清素增强了群居蝗虫的独居性。血清素可能调节蝗虫相变过程中表现出的类似退缩的行为模式，并且这种机制在不同蝗虫物种中是保守的。
