Chin Eunice H, Shah Amit H, Schmidt Kim L, Sheldon Lani D, Love Oliver P, Soma Kiran K
Department of Zoology, University of British Columbia, 6270 University Blvd., Vancouver, BC, Canada.
Horm Behav. 2008 Jun;54(1):194-202. doi: 10.1016/j.yhbeh.2008.02.014. Epub 2008 Mar 6.
Sexual differentiation of the brain has traditionally been thought to be driven by gonadal hormones, particularly testosterone (T). Recent studies in songbirds and other species have indicated that non-gonadal sex steroids may also be important. For example, dehydroepiandrosterone (DHEA)--a sex steroid precursor that can be synthesized in the adrenal glands and/or brain--can be converted into active sex steroids, such as 17beta-estradiol (E(2)), within the brain. Here, we examine plasma DHEA and E(2) levels in wild developing European starlings (Sturnus vulgaris), from hatch (P0) to fledging (P20). Blood samples were collected from either the brachial vein (n=143) or the jugular vein (n=129). In songbirds, jugular plasma is enriched with neurally-synthesized steroids and, therefore, jugular plasma is an indirect measure of the neural steroidal milieu. Interestingly, brachial DHEA levels were higher in males than females at P4. In contrast, jugular DHEA levels were higher in females than males at P0 and P10. Brachial E(2) levels were higher in males than females at P6. Surprisingly, jugular E(2) levels were not high and showed no sex differences. Also, we calculated the difference between brachial and jugular steroid levels. At several ages, jugular steroid levels were lower than brachial levels, particularly in males, suggesting greater neural metabolism of circulating DHEA and E(2) in males than females. At a few ages, jugular steroid levels were higher than brachial levels, suggesting neural secretion of DHEA or E(2) into the general circulation. Taken together, these data suggest that DHEA may play a role in brain sexual differentiation in songbirds.
传统观点认为，大脑的性别分化是由性腺激素驱动的，尤其是睾酮（T）。最近对鸣禽和其他物种的研究表明，非性腺来源的性类固醇可能也很重要。例如，脱氢表雄酮（DHEA）——一种可在肾上腺和/或大脑中合成的性类固醇前体——可在大脑中转化为活性性类固醇，如17β-雌二醇（E₂）。在此，我们检测了野生欧洲椋鸟（Sturnus vulgaris）从孵化（P0）到羽翼丰满（P20）发育过程中的血浆DHEA和E₂水平。从肱静脉（n = 143）或颈静脉（n = 129）采集血样。在鸣禽中，颈静脉血浆富含神经合成的类固醇，因此，颈静脉血浆是神经甾体环境的间接指标。有趣的是，在P4时，雄性的肱静脉DHEA水平高于雌性。相反，在P0和P10时，雌性的颈静脉DHEA水平高于雄性。在P6时，雄性的肱静脉E₂水平高于雌性。令人惊讶的是，颈静脉E₂水平不高且无性别差异。此外，我们计算了肱静脉和颈静脉类固醇水平的差异。在几个年龄段，颈静脉类固醇水平低于肱静脉水平，尤其是在雄性中，这表明雄性循环中的DHEA和E₂的神经代谢比雌性更强。在少数几个年龄段，颈静脉类固醇水平高于肱静脉水平，这表明DHEA或E₂从神经分泌进入体循环。综上所述，这些数据表明DHEA可能在鸣禽大脑的性别分化中发挥作用。
