Johnson A E
Karolinska Institute, Huddinge Hospital, Sweden.
Ann N Y Acad Sci. 1992 Jun 12;652:357-73. doi: 10.1111/j.1749-6632.1992.tb34367.x.
In the previous sections, data were presented on the regulation of OT receptor binding by gonadal hormones. However, it is important to emphasize that gonadal steroids and E2 in particular also regulate other facets of OT transmission. For example, OT peptide levels as indicated by mRNA levels and OT immunoreactivity are enhanced by gonadal steroids. Similarly, OT release is also influenced by circulating steroids. By focusing on data collected in female rats and combining these different factors, the following relationships emerge. Within the ventromedial hypothalamus, OT peptide levels are virtually undetectable and OT receptor binding is negligible in the absence of E2. As circulating levels of E2 rise, increases in OT immunoreactivity and OT-receptor binding in the ventromedial hypothalamus and in the VMN itself can be detected. Under these conditions, OT receptor binding in and around the vl-VMN is markedly increased, rendering cells in the vl-VMN responsive to OT stimulation. Significantly, this increased responsivity is most evident at low concentrations of OT. With further increases in E2, P4 is released from the ovary, resulting in a number of biochemical changes in the central nervous system, including a potentiation of the effects of E2 on hypothalamic OT-receptor binding. Within a few hours after the initiation of P4 release, sexual receptivity can be elicited. At this time, sexual contact by the male enhances OT-peptide levels in the ventromedial hypothalamus of steroid-primed female rats, which in turn potentiates the display of sexual receptivity. The model outlined above not only summarizes a large portion of the data on steroid regulation of hypothalamic OT receptors, but more importantly, serves to highlight areas that require additional study. One important question that remains to be resolved is the source of OT receptors in the ventromedial hypothalamus. While the lesion studies discussed above indicate that the majority of fibers in the ventrolateral hypothalamus originate in the VMN, definitive results can only be obtained with more direct methods. For example, following the eventual cloning and sequencing of the OT receptor, studies on the distribution and regulation of OT receptor mRNA could be conducted to determine the hypothalamic cells that synthesize OT receptors. Complementary experiments that employ an immunohistological approach in combination with electron microscopy could be used to visualize the region(s) of the cell that react to OT receptor antibodies. Additional studies are also required to determine the role of steroid-modulated OT receptor binding in the hypothalamus of male rats.(ABSTRACT TRUNCATED AT 400 WORDS)
在前几节中，展示了有关性腺激素对催产素（OT）受体结合调节的数据。然而，必须强调的是，性腺类固醇尤其是雌二醇（E2）也调节OT传递的其他方面。例如，性腺类固醇可提高由mRNA水平和OT免疫反应性所指示的OT肽水平。同样，OT释放也受循环类固醇的影响。通过关注在雌性大鼠中收集的数据并综合这些不同因素，出现了以下关系。在腹内侧下丘脑内，在没有E2的情况下，OT肽水平几乎检测不到，OT受体结合也可忽略不计。随着E2循环水平的升高，可检测到腹内侧下丘脑和室旁核（VMN）本身中OT免疫反应性和OT受体结合增加。在这些条件下，腹外侧室旁核（vl-VMN）及其周围的OT受体结合显著增加，使vl-VMN中的细胞对OT刺激有反应。重要的是，这种增加的反应性在低浓度OT时最为明显。随着E2的进一步增加，卵巢释放孕酮（P4），导致中枢神经系统发生一系列生化变化，包括增强E2对下丘脑OT受体结合的作用。在P4释放开始后的几个小时内，可引发性接受能力。此时，雄性的性接触会提高经类固醇预处理的雌性大鼠腹内侧下丘脑中的OT肽水平，这反过来又增强了性接受能力的表现。上述模型不仅总结了关于下丘脑OT受体类固醇调节的大部分数据，更重要的是，有助于突出需要进一步研究的领域。一个有待解决的重要问题是腹内侧下丘脑中OT受体的来源。虽然上述损伤研究表明下丘脑外侧的大多数纤维起源于VMN，但只有采用更直接的方法才能获得确切结果。例如，在OT受体最终克隆和测序之后，可以进行关于OT受体mRNA分布和调节的研究，以确定合成OT受体的下丘脑细胞。采用免疫组织学方法结合电子显微镜的补充实验可用于观察细胞中与OT受体抗体反应的区域。还需要进行更多研究以确定类固醇调节的OT受体结合在雄性大鼠下丘脑中的作用。（摘要截取自400字）
