Department of Zoology, Michigan State University, East Lansing, MI, USA.
J Neuroendocrinol. 2012 Sep;24(9):1213-21. doi: 10.1111/j.1365-2826.2012.02328.x.
Neural steroids, as well as the enzymes that produce these hormones, are important for sexual differentiation of the brain during development. Aromatase converts testosterone into oestradiol. 5α-reductase converts testosterone to 5α-dihydrotestosterone and occurs in two isozymes: type 1 (5αR1) and type 2 (5αR2). Each of these enzymes is present in the developing brain in many species, although no work has been carried out examining the expression of all three enzymes in non-avian reptiles with genetic sex determination. In the present study, we evaluated mRNA expression of neural aromatase, 5αR1 and 5αR2, on the day of hatching and at day 50 in one such lizard, the green anole. We describe the distribution of these enzymes throughout the brain and the quantification of mRNA expression in three regions that control adult sexual behaviours: the preoptic area (POA) and ventromedial amygdala (AMY), which are involved in male displays, as well as the ventromedial hypothalamus, which regulates female receptivity. Younger animals had a greater number (POA) and density (AMY) of 5αR1 mRNA expressing cells. We detected no effects of sex or age on aromatase or 5αR2. In comparison with data from adults, the present results support the idea that the green anole forebrain has not completely differentiated by 50 days after hatching and that 5αR1 may play a role in the early development of regions important for masculine function.
神经甾体以及产生这些激素的酶对于发育过程中大脑的性分化很重要。芳香酶将睾酮转化为雌二醇。5α-还原酶将睾酮转化为 5α-二氢睾酮，有两种同工酶：1 型（5αR1）和 2 型（5αR2）。尽管尚未对具有遗传性别决定的非鸟类爬行动物中所有三种酶的表达进行研究，但这些酶在许多物种的发育大脑中都存在。在本研究中，我们评估了在孵化当天和 50 天时，一种蜥蜴，绿鬣蜥中的神经芳香酶、5αR1 和 5αR2 的 mRNA 表达。我们描述了这些酶在大脑中的分布，并在三个控制成年性行为的区域中对 mRNA 表达进行了定量：参与雄性展示的视前区（POA）和腹侧杏仁核（AMY），以及调节雌性接受性的腹侧下丘脑。年幼的动物具有更多的 5αR1 mRNA 表达细胞（POA）和密度（AMY）。我们没有发现性别或年龄对芳香酶或 5αR2 的影响。与成人数据相比，本研究结果支持绿鬣蜥前脑在孵化后 50 天尚未完全分化的观点，并且 5αR1 可能在对雄性功能重要的区域的早期发育中发挥作用。
