Data from: Differential activation of serotonergic neurones during short- and long-term gregarisation of desert locusts

Serotonin is an evolutionarily conserved neurochemical with extensive roles in orchestrating nervous system function and behavioural plasticity. A dramatic example is the rapid transformation of desert locusts from cryptic asocial animals into gregarious crop pests. This transformation is triggered by forced contact between individuals that in turn induces a surge in serotonin within their thoracic ganglia. To identify the neurones responsible for this plasticity-inducing surge, we analysed how acute exposure to three gregarising stimuli — crowding, touching the hind legs, or seeing and smelling other locusts — and prolonged group-living affect the expression of serotonin in the thoracic ganglia. Quantitative analysis of cell body immunofluorescence revealed three classes of neurones with distinct expressional responses. All ganglia contained neurones that responded to multiple gregarising stimuli with increased expression. This included a single prominent cell in the metathoracic ganglion. A second class showed increased expression only in response to intense visual and olfactory stimuli from conspecifics. Prolonged group living affected a third and entirely different set of neurones, revealing a two-tiered role of the serotonergic system as both initiator and substrate of socially induced plasticity. This demonstrates the critical importance of ontogenetic time for understanding the function of serotonin in the reorganization of behaviour.

5-羟色胺（Serotonin）是一类进化保守的神经化学物质，在调控神经系统功能与行为可塑性方面发挥着广泛作用。其中极具代表性的案例便是沙漠蝗的快速行为与形态转变——从隐蔽独居的生物蜕变为群居性农业害虫。该转变由个体间的强制接触触发，进而引发其胸神经节（thoracic ganglia）内5-羟色胺水平的激增。为明确介导该可塑性诱导激增的神经元，本研究分析了急性暴露于三类促群居刺激（高密度拥挤、触碰后足，以及感知同类的视觉与嗅觉信号），以及长期群居状态，对胸神经节内5-羟色胺表达的影响。通过对细胞体免疫荧光信号的定量分析，我们发现了三类具有截然不同表达响应模式的神经元：所有神经节均存在可响应多种促群居刺激并上调表达的神经元，其中包括后胸神经节（metathoracic ganglion）内的单个标志性神经元；第二类神经元仅在感知同类发出的强烈视觉与嗅觉刺激时，才会出现表达上调；而长期群居则会影响第三类完全不同的神经元群，这揭示了5-羟色胺能系统（serotonergic system）兼具社会诱导可塑性的引发者与作用基质的双重功能。本研究证实了个体发育时间（ontogenetic time）在解析5-羟色胺调控行为重组织功能中的关键作用。