Kohama S G, Bethea C L
Division of Reproductive Sciences, Oregon Regional Primate Research Center, Beaverton 97006.
Endocrinology. 1995 Apr;136(4):1790-800. doi: 10.1210/endo.136.4.7895692.
PRL release in primates can be stimulated by progesterone (P) after estrogen (E) priming. Hypothalamic dopaminergic neurons are a primary inhibitory system of PRL secretion, which differentially express progestin receptors (PR) in a cell-specific manner. Thus, these neurons may be an important target of P for increasing PRL. To further this hypothesis, two studies were performed. First, verification of the subpopulations of dopaminergic neurons that express PR was obtained with a combination of immunocytochemistry for PR and in situ hybridization for tyrosine hydroxylase (TH). Second, the effects of E and E plus P on the expression of TH messenger RNA (mRNA) were examined with in situ hybridization and image analysis in five different subpopulations of dopaminergic neurons. In the first study, dual labeled neurons were found rostrally around the ventral portion of the third ventricle and in more caudal periventricular areas, including the dorsal arcuate nucleus. Little or no PR were observed in TH-positive neurons located in the lateral chiasmatic area, paraventricular nucleus, ventral arcuate nucleus, or the substantia nigra. These results are consistent with our previous observations using double immunocytochemistry. In the second study, there was no significant effect of E or E plus P on single cell levels of TH mRNA in dopaminergic neurons of the subventricular area, periventricular area, or paraventricular nucleus. However, E plus P treatment produced a significant decrease in TH mRNA in the ventral arcuate dopaminergic neurons. There was no effect of E or E plus P in the dorsal arcuate dopaminergic neurons. In conclusion, E plus P decreases the expression of TH mRNA in the ventral arcuate dopaminergic neurons, a subpopulation that rarely expresses PR. The decrease in TH mRNA in the ventral arcuate dopaminergic neurons after E and P treatment is consistent with a role for this subpopulation of tuberoinfundibular neurons in P-induced PRL secretion.
在灵长类动物中，雌激素（E）预处理后，孕激素（P）可刺激催乳素（PRL）释放。下丘脑多巴胺能神经元是PRL分泌的主要抑制系统，其以细胞特异性方式差异表达孕激素受体（PR）。因此，这些神经元可能是P增加PRL的重要靶点。为进一步验证这一假说，进行了两项研究。首先，通过PR免疫细胞化学和酪氨酸羟化酶（TH）原位杂交相结合的方法，对表达PR的多巴胺能神经元亚群进行了验证。其次，利用原位杂交和图像分析技术，研究了E和E加P对五个不同多巴胺能神经元亚群中TH信使核糖核酸（mRNA）表达的影响。在第一项研究中，在第三脑室腹侧部分周围的吻侧以及包括背侧弓状核在内的更尾侧的室周区域发现了双标记神经元。在位于外侧视交叉区、室旁核、腹侧弓状核或黑质的TH阳性神经元中，几乎未观察到PR。这些结果与我们之前使用双重免疫细胞化学的观察结果一致。在第二项研究中，E或E加P对室下区多巴胺能神经元、室周区或室旁核中TH mRNA的单细胞水平没有显著影响。然而，E加P处理使腹侧弓状多巴胺能神经元中的TH mRNA显著降低。E或E加P对背侧弓状多巴胺能神经元没有影响。总之，E加P降低了腹侧弓状多巴胺能神经元中TH mRNA的表达，该亚群很少表达PR。E和P处理后腹侧弓状多巴胺能神经元中TH mRNA的降低与该下丘脑漏斗神经元亚群在P诱导的PRL分泌中的作用一致。
