Data from: Efficacy of negative feedback in the HPA axis predicts recovery from acute challenges.

The glucocorticoid stress response mediates a suite of physiological and behavioral changes that allow vertebrates to cope with transient stressors. Chronically elevated glucocorticoid levels are known to result in a variety of organismal costs, but relatively little is known about the downstream effects of mounting a series of brief, acute spikes in circulating glucocorticoids. Conceptual models of stress suggest that repeated acute stressors might produce ‘wear-and-tear’ on the stress response system when encountered in sequence. We used a novel technique to experimentally induce acute corticosterone spikes on either three or six consecutive days in incubating tree swallows. Consistent with the ‘wear-and-tear’ hypothesis, we found that i) a sequence of corticosterone spikes produced cumulative effects on corticosterone regulation, ii) treatment frequency predicted the severity of consequences, and iii) individual variation in the ability to terminate the stress response through negative feedback predicted the duration of physiological disruption in the group that experienced the most frequent challenges. Our results illustrate the importance of assessing multiple aspects of the hormonal stress response and have implications for understanding both individual and population resilience to repeated transient stressors.

糖皮质激素（glucocorticoid）应激反应介导一系列生理与行为变化，使脊椎动物得以应对短暂应激源。已知长期升高的糖皮质激素水平会引发多种机体损耗，但目前对于循环中糖皮质激素出现一系列短暂急性峰值后的下游效应，相关研究仍较为匮乏。应激反应的概念模型指出，若连续遭遇反复急性应激源，可能会对应激反应系统造成“磨损损耗”。本研究采用一种新型实验技术，在孵卵期树燕身上连续3天或6天诱导产生急性皮质酮（corticosterone）峰值。与“磨损损耗”假说一致，本研究发现：其一，皮质酮峰值序列会对皮质酮调控产生累积效应；其二，处理频率与后果严重程度呈正相关；其三，在应激挑战最频繁的组别中，个体通过负反馈终止应激反应的能力差异，可预测生理紊乱的持续时长。本研究结果凸显了评估激素应激反应多维度特征的重要性，同时为理解个体与种群对反复短暂应激源的恢复力提供了理论参考。