Scotti Melissa-Ann L, Rendon Nikki M, Greives Timothy J, Romeo Russell D, Demas Gregory E
Department of Psychology, Northern Illinois University, DeKalb, Illinois.
Department of Biology, Program in Neuroscience, Center for the Integrative Study of Animal Behavior, Indiana University, Bloomington, Indiana.
J Exp Zool A Ecol Genet Physiol. 2015 Jun;323(5):331-41. doi: 10.1002/jez.1922. Epub 2015 Mar 19.
Testosterone mediates aggression in many vertebrates. In some species, aggression remains high during the non-breeding season (e.g., winter), when testosterone levels are low. In Siberian hamsters (Phodopus sungorus), we have demonstrated photoperiodic changes in aggression with hamsters housed in short, "winter-like" days displaying significantly more territorial aggression than long-day animals, despite low levels of testosterone. The mechanisms by which photoperiod regulates aggression, however, remain largely unknown. Adrenocortical hormones (e.g., glucocorticoids) have been implicated in mediating seasonal aggression; circulating concentrations of these hormones have been correlated with aggression in some species. The goal of this study was to examine the role of cortisol and glucocorticoid receptors in mediating photoperiodic changes in aggression in male Siberian hamsters. Males were housed in long or short days and treated with either exogenous cortisol or vehicle. Circulating levels of cortisol, adrenal cortisol content, and aggression were quantified. Lastly, photoperiodic effects on glucocorticoid receptor (GR) protein levels were quantified in limbic brain regions associated with aggression, including medial prefrontal cortex, amygdala, and hippocampus. Short-day hamsters were more aggressive than long-day hamsters, however cortisol treatment did not affect aggression. Photoperiod had no effect on serum or adrenal cortisol or GR levels in the brain regions examined. Taken together, these data suggest that increases in cortisol levels do not cause increases associated with short-day aggression, and further that GR protein levels are not associated with photoperiodic changes in aggression. The results of this study contribute to our understanding of the role of adrenocortical steroids in mediating seasonal aggression.
睾酮在许多脊椎动物中介导攻击行为。在一些物种中，在非繁殖季节（如冬季），当睾酮水平较低时，攻击行为仍然很高。在西伯利亚仓鼠（Phodopus sungorus）中，我们已经证明了攻击行为的光周期变化，即处于短的、“类似冬季”日照时长下的仓鼠比长日照动物表现出显著更多的领地攻击性，尽管其睾酮水平较低。然而，光周期调节攻击行为的机制在很大程度上仍然未知。肾上腺皮质激素（如糖皮质激素）被认为参与介导季节性攻击行为；这些激素的循环浓度在一些物种中与攻击行为相关。本研究的目的是检查皮质醇和糖皮质激素受体在介导雄性西伯利亚仓鼠攻击行为的光周期变化中的作用。雄性仓鼠被饲养在长日照或短日照条件下，并分别给予外源性皮质醇或赋形剂。对皮质醇的循环水平、肾上腺皮质醇含量和攻击行为进行了量化。最后，在与攻击行为相关的边缘脑区，包括内侧前额叶皮质、杏仁核和海马体中，对光周期对糖皮质激素受体（GR）蛋白水平的影响进行了量化。短日照仓鼠比长日照仓鼠更具攻击性，然而皮质醇处理并未影响攻击行为。光周期对所检查脑区的血清或肾上腺皮质醇或GR水平没有影响。综上所述，这些数据表明皮质醇水平的升高不会导致与短日照攻击行为相关的增加，并且进一步表明GR蛋白水平与攻击行为的光周期变化无关。本研究结果有助于我们理解肾上腺皮质类固醇在介导季节性攻击行为中的作用。
