Boonstra Rudy, Lane Jeffrey E, Boutin Stan, Bradley Adrian, Desantis Lanna, Newman Amy E M, Soma Kiran K
Centre for the Neurobiology of Stress, Department of Biological Sciences, University of Toronto Scarborough, 1265 Military Trail, Toronto, Ont., Canada M1C 1A4.
Gen Comp Endocrinol. 2008 Aug;158(1):61-7. doi: 10.1016/j.ygcen.2008.05.004. Epub 2008 May 11.
In many species, territorial behavior is limited to the breeding season and is tightly coupled to circulating gonadal steroid levels. In contrast, both male and female red squirrels (Tamiasciurus hudsonicus) are highly aggressive in both the breeding and non-breeding seasons in defense of food stores on their individual territories throughout the boreal and northern forests of North America. Dehydroepiandrosterone (DHEA), an androgen precursor, is secreted from the adrenal cortex in some mammals, and DHEA has been linked to aggression in non-breeding songbirds. Here, we examined plasma DHEA levels in a natural population of red squirrels in the Yukon, Canada. Plasma DHEA levels in both males and females reached high concentrations (up to 16.952 ng/ml in males and 14.602 ng/ml in females), markedly exceeding plasma DHEA concentrations in laboratory rats and mice and similar to plasma DHEA concentrations in some primates. Circulating DHEA levels showed both seasonal and yearly variation. Seasonal variation in male plasma DHEA levels was negatively correlated with testes mass. Yearly variation in male DHEA levels was positively correlated with population density. In both males and females, circulating DHEA rapidly increased after ACTH treatment, implying an adrenal origin. This is the first examination of plasma DHEA concentrations in a wild rodent and the first field experiment on the regulation of plasma DHEA in any wild mammal. These data lay the foundation for future studies on the role of DHEA in non-breeding territoriality in this species and other mammals.
在许多物种中，领地行为仅限于繁殖季节，并且与循环的性腺类固醇水平紧密相关。相比之下，北美北方和北部森林中，雄性和雌性红松鼠（北美红松鼠）在繁殖和非繁殖季节都会为保卫各自领地内的食物储备而表现出高度攻击性。脱氢表雄酮（DHEA），一种雄激素前体，在一些哺乳动物中由肾上腺皮质分泌，并且DHEA与非繁殖鸣禽的攻击性有关。在此，我们检测了加拿大育空地区自然种群红松鼠的血浆DHEA水平。雄性和雌性的血浆DHEA水平均达到高浓度（雄性高达16.952 ng/ml，雌性高达14.602 ng/ml），明显超过实验室大鼠和小鼠的血浆DHEA浓度，与一些灵长类动物的血浆DHEA浓度相似。循环DHEA水平呈现季节性和年度变化。雄性血浆DHEA水平的季节性变化与睾丸质量呈负相关。雄性DHEA水平的年度变化与种群密度呈正相关。在雄性和雌性中，ACTH处理后循环DHEA迅速增加，这意味着其来源于肾上腺。这是首次对野生啮齿动物血浆DHEA浓度进行检测，也是首次在任何野生哺乳动物中进行关于血浆DHEA调节的野外实验。这些数据为未来研究DHEA在该物种及其他哺乳动物非繁殖领地行为中的作用奠定了基础。
