Crews David, Gill Cynthia J, Wennstrom Kira L
Section of Integrative Biology, University of Texas at Austin, Institute for Neuroscience, Austin, TX 78712, USA.
Brain Res. 2004 Apr 9;1004(1-2):136-41. doi: 10.1016/j.brainres.2003.11.076.
Female, but not male, whiptail lizards will respond to exogenous estrogen with an increase in estrogen receptor alpha (ER alpha) mRNA in the ventromedial hypothalamus (VMH). The current study tested whether differences in long-term testosterone exposure may be responsible for this sex difference. In the first experiment, female whiptails were gonadectomized and implanted for 6 weeks with either a Silastic capsule containing testosterone or an empty capsule after which the implant was removed. In a second experiment, male whiptail lizards were castrated for 1 week or for 6 weeks. In both experiments animals were then injected with either estradiol benzoate or steroid suspension vehicle and the brains collected 24 h later. Brain mRNA expression was assayed using in situ hybridization. Chronic testosterone treatment reduced estrogen-induced ER alpha mRNA levels (number of grains per cell) in the VMH in females. In contrast, there were no significant effects of time after castration or estrogen treatment on induction of ER alpha mRNA in the VMH in males. The abundance of estrogen-induced ER alpha mRNA in the VMH, therefore, appears to be responsive to testosterone environment in the female but not in the male, suggesting a difference in this species between the sexes in the mechanism of steroid receptor regulation.
雌性鞭尾蜥而非雄性鞭尾蜥，会对外源性雌激素作出反应，其腹内侧下丘脑（VMH）中的雌激素受体α（ERα）mRNA会增加。当前的研究测试了长期睾酮暴露的差异是否可能导致这种性别差异。在第一个实验中，对雌性鞭尾蜥进行性腺切除，并植入含睾酮的硅胶胶囊或空胶囊6周，之后取出植入物。在第二个实验中，对雄性鞭尾蜥进行1周或6周的去势。在两个实验中，随后给动物注射苯甲酸雌二醇或类固醇悬浮液载体，并在24小时后收集大脑。使用原位杂交法检测大脑mRNA表达。长期睾酮处理降低了雌性VMH中雌激素诱导的ERαmRNA水平（每个细胞的颗粒数）。相比之下，去势时间或雌激素处理对雄性VMH中ERαmRNA的诱导没有显著影响。因此，VMH中雌激素诱导的ERαmRNA丰度似乎对雌性的睾酮环境有反应，而对雄性则无反应，这表明该物种在类固醇受体调节机制上存在性别差异。
