School of Life Sciences, Arizona State University, Tempe, AZ 85287-4501, USA.
Horm Behav. 2012 May;61(5):741-9. doi: 10.1016/j.yhbeh.2012.03.012. Epub 2012 Apr 1.
The Challenge Hypothesis postulates that male vertebrates can respond to social challenges, such as simulated territorial intrusions, by rapidly increasing their concentrations of plasma androgens, such as testosterone (T). This increase may facilitate the expression of aggressive behavior and lead to persistence of this behavior even after withdrawal of the challenge, thus potentially promoting territoriality and the probability of winning future challenges. The scope of the Challenge Hypothesis was tested by exposing free-ranging male Cassin's Sparrows, Peucaea cassinii, to conspecific song playback (SPB) at the beginning of the vernal nesting season. Exposure to SPB stimulated aggressive behavior but did not influence plasma T. Furthermore, plasma T did not correlate with the duration of exposure to SPB, and the behavioral response to SPB did not differ in males that were challenged a second time shortly after the first challenge. As birds were investigated at a stage of their reproductive cycle when plasma T is presumably seasonally high due to photostimulation, the lack of hormonal response to SPB may have been due to the hypothalamus-pituitary-gonadal axis secreting hormones at maximum rates. This was not the case, however, because administration of gonadotropin-releasing hormone I rapidly stimulated the secretion of luteinizing hormone (LH) and T, and treatment with ovine LH rapidly stimulated T secretion.
挑战假说认为，雄性脊椎动物可以对社会挑战做出反应，例如模拟领地入侵，迅速增加其血浆雄激素（如睾酮（T））的浓度。这种增加可能有助于表现出攻击行为，并导致这种行为在挑战结束后持续存在，从而可能促进领地性和赢得未来挑战的可能性。挑战假说的范围通过在春季筑巢季节开始时，将自由生活的卡辛氏雀（Cassin's Sparrow，Peucaea cassinii）雄性暴露于同种鸟鸣（SPB）中进行了测试。暴露于 SPB 会刺激攻击行为，但不会影响血浆 T。此外，血浆 T 与暴露于 SPB 的时间长短无关，并且在第一次挑战后不久再次受到挑战的雄性中，对 SPB 的行为反应没有差异。由于鸟类在繁殖周期的一个阶段被调查，此时由于光刺激，血浆 T 可能因季节性升高，因此对 SPB 没有荷尔蒙反应可能是由于下丘脑-垂体-性腺轴以最大速度分泌荷尔蒙。然而，事实并非如此，因为促性腺激素释放激素 I 的给药会迅速刺激黄体生成素（LH）和 T 的分泌，而绵羊 LH 的处理会迅速刺激 T 的分泌。
