Data from: Cooperative defence operates by social modulation of biogenic amine levels in the honeybee brain

The defence of a society often requires that some specialized members coordinate to repel a threat at personal risk. This is especially true for honeybee guards, which defend the hive and may sacrifice their lives upon stinging. Central to this cooperative defensive response is the sting alarm pheromone, which has isoamyl acetate (IAA) as its main component. Although this defensive behaviour has been well described, the neural mechanisms triggered by IAA to coordinate stinging have long remained unknown. Here we show that IAA upregulates brain levels of serotonin and dopamine, thereby increasing the likelihood of an individual bee to attack and sting. Pharmacological enhancement of the levels of both amines induces higher defensive responsiveness, while decreasing them via antagonists decreases stinging. Our results thus uncover the neural mechanism by which an alarm pheromone recruits individuals to attack and repel a threat, and suggest that the alarm pheromone of honeybees acts on their response threshold rather than as a direct trigger.社群防御往往需要部分特化成员协同行动，以承担个体风险击退外来威胁。这一点在守卫蜂身上体现得尤为突出：它们负责守卫蜂巢，蜇刺外敌后往往会付出生命代价。介导这类协同防御反应的核心物质是蜇刺告警信息素（sting alarm pheromone），其主要成分为乙酸异戊酯（isoamyl acetate, IAA）。尽管这类防御行为已被充分阐释，但IAA触发协调蜇刺行为的神经机制长期以来仍未明晰。本研究发现，IAA可上调蜜蜂脑部的5-羟色胺（serotonin）与多巴胺（dopamine）水平，进而提升个体蜜蜂发起攻击并蜇刺的概率。通过药理学手段提升这两种胺类的水平可增强防御反应活性，而通过拮抗剂降低其水平则会减少蜇刺行为的发生频次。因此，本研究结果揭示了告警信息素招募个体发起攻击、击退威胁的神经机制，并表明蜜蜂的告警信息素并非直接触发行为，而是通过调节个体的行为反应阈值发挥调控作用。