Organisms must constantly adapt to changes in their environment to survive. It is thought that neuromodulators such as serotonin enable sensory neurons to better process input encountered during different behavioral contexts. Here, we investigated how serotonergic innervation affects neural and behavioral responses to behaviorally relevant envelope stimuli in the weakly electric fish species Apteronotus albifrons. Under baseline conditions, we found that exogenous serotonin application within the electrosensory lateral line lobe increased sensory neuron excitability, thereby promoting burst firing. We found that serotonin enhanced the responses to envelope stimuli of pyramidal cells within the lateral segment of the electrosensory lateral line lobe (ELL) by increasing sensitivity, with the increase more pronounced for stimuli with higher temporal frequencies (i.e., >0.2 Hz). Such increases in neural sensitivity were due to increased burst firing. At the organismal level, bilateral serotonin application within the ELL lateral segment enhanced behavioral responses to sensory input through increases in sensitivity. Similar to what was observed for neural responses, increases in behavioral sensitivity were more pronounced for higher (i.e., >0.2 Hz) temporal frequencies. Surprisingly, a comparison between our results and previous ones obtained in the closely related species A. leptorhynchus revealed that, while serotonin application gave rise to similar effects on neural excitability and responses to sensory input, serotonin application also gave rise to marked differences in behavior. Specifically, behavioral responses in A. leptorhynchus were increased primarily for lower (i.e., ≤0.2 Hz) rather than for higher temporal frequencies. Thus, our results strongly suggest that there are marked differences in how sensory neural responses are processed downstream to give rise to behavior across both species. This is even though previous results have shown that the behavioral responses of both species to envelope stimuli were identical when serotonin is not applied.

生物必须不断适应环境变化才能生存。据认为，诸如5-羟色胺的神经调节剂使感觉神经元能够更好地处理在不同行为情况下遇到的输入。在这里，我们调查了血清素能神经支配如何影响对弱电鱼物种中与行为相关的包膜刺激的神经和行为反应拟南芥。在基线条件下，我们发现外源性5-羟色胺在电感觉侧叶内的应用增加了感觉神经元的兴奋性，从而促进了爆发放电。我们发现，5-羟色胺通过增加敏感性来增强对电感觉侧线叶（ELL）侧向部分内锥体细胞包膜刺激的响应，对于更高的时间频率（即> 0.2 Hz）的刺激，其增加更为明显。神经敏感性的这种增加是由于爆发力增加引起的。在生物水平上，通过提高敏感性，在ELL侧段内应用双侧5-羟色胺可增强对感觉输入的行为反应。与观察到的神经反应相似，行为敏感性的增加越高越明显（即> 0）。2 Hz）时间频率。令人惊讶的是，我们的结果与先前在紧密相关物种中获得的结果进行了比较细支气管假单胞菌揭示了，尽管应用5-羟色胺对神经兴奋性和对感觉输入的反应产生了相似的影响，但应用5-羟色胺也引起了行为上的明显差异。具体来说，细支气管假单胞菌频率的增加主要是针对较低的频率（即≤0.2Hz），而不是较高的时间频率。因此，我们的结果有力地表明，在下游处理感官神经反应的方式上存在明显差异，从而引起了两个物种的行为。即使以前的结果表明，当不使用5-羟色胺时，两个物种对包膜刺激的行为反应是相同的。