Department of Zoology and Entomology, University of Pretoria, 0028 Pretoria, South Africa.
J Chem Neuroanat. 2018 Dec;94:1-7. doi: 10.1016/j.jchemneu.2018.08.002. Epub 2018 Aug 15.
The eusocial Damaraland mole-rat (Fukomys damarensis) represents an extreme example of reproductive skew, in that reproduction is completely blocked in female subordinate group members. It is thought that in these animals normal GnRH secretion from the hypothalamus is disrupted. Prolactin, a peptide hormone secreted from the anterior pituitary gland, has been implicated in a wide variety of functions. Well documented in rodents is its role in mediating lactational infertility. Elevated circulating prolactin levels, such as during lactation, are associated with reduced GnRH release into the portal blood and with a reduction in the frequency and amplitude of LH pulses. The present study aimed at investigating whether such a mechanism could act in reproductively suppressed female Damaraland mole-rats. By means of in situ hybridisation we studied the distribution and gene expression of the prolactin receptor (Prlr) in wild-caught female Damaraland mole-rats with different reproductive status. Substantial Prlr expression was found in several brain regions, with highest levels in the choroid plexus and moderate expression in the preoptic and tuberal hypothalamus. While in reproductive and non-reproductive females plasma prolactin levels were very low and not significantly different, quantification of the Prlr hybridisation signal revealed significant differences in relation to reproductive status. Reproductively suppressed females had increased expression of Prlr in the choroid plexus and in the arcuate nucleus (ARC) when compared to reproductive females. This suggests higher local prolactin levels in the brain of suppressed females. Together with previous findings, it could indicate that prolactin inhibits ARC kisspeptin neurons, which then would lead to reduced activation of GnRH neurons in such females.
穴居的东非滨鼠（Fukomys damarensis）是生殖偏斜的极端例子，因为雌性从属群体成员的生殖完全被阻断。人们认为，在这些动物中，下丘脑正常的 GnRH 分泌被打乱。催乳素是一种由垂体前叶分泌的肽类激素，它在各种功能中都有涉及。在啮齿动物中，其在介导哺乳期不孕方面的作用已有充分的记录。循环中的催乳素水平升高，如在哺乳期，与 GnRH 向门脉血液中的释放减少以及 LH 脉冲的频率和幅度降低有关。本研究旨在研究这种机制是否可以作用于生殖受抑制的东非滨鼠。通过原位杂交，我们研究了不同生殖状态的野生捕获雌性东非滨鼠中催乳素受体（Prlr）的分布和基因表达。Prlr 在几个脑区表达丰富，脉络丛中的表达最高，视前核和结节下丘脑的表达中等。虽然生殖和非生殖雌性的血浆催乳素水平非常低且没有显著差异，但 Prlr 杂交信号的定量分析显示与生殖状态相关的显著差异。与生殖雌性相比，生殖受抑制的雌性在脉络丛和弓状核（ARC）中 Prlr 的表达增加。这表明抑制雌性的大脑中存在更高水平的局部催乳素。结合先前的发现，这可能表明催乳素抑制了 ARC 促性腺激素释放肽神经元，从而导致这些雌性中 GnRH 神经元的激活减少。
