Department of Anatomy, Porto Medical School, University of Porto, Alameda Hernâni Monteiro, 4200-319 Porto, Portugal.
Brain Res. 2010 Dec 17;1366:60-70. doi: 10.1016/j.brainres.2010.10.043. Epub 2010 Oct 20.
The effects of estrogens on the ventrolateral division of the hypothalamic ventromedial nucleus (VMNvl) are essential for its role in the regulation of female sexual behavior. Enhanced synaptogenesis and induction of progesterone receptors (PRs) are hallmarks of the actions of estrogens on the VMNvl. To investigate the influence of neural afferents in mediating these effects, we estimated the number of spine and dendritic synapses per neuron and the total number of PR-immunoreactive neurons in ovariectomized rats treated with either estradiol benzoate or vehicle, after unilateral VMN deafferentation. The estimates were performed independently in the VMNvl of the deafferented and contralateral sides, and in the VMNvl of unoperated rats (controls). The administration of estradiol benzoate did not induce any increase in the number of synapses of the deafferented VMNvl. In the contralateral VMNvl, the synaptogenic effects of estrogen were apparent, but still reduced relative to the control VMNvl, where a 25% increase in the total number of synapses was observed after estrogenic stimulation. In the absence of estrogenic stimulation, i.e., in basal conditions, deafferentation reduced the number of dendritic and spine synapses, but particularly the latter. The reduction was also visible, but less marked, in the contralateral VMNvl. Contrary to synapses, the estrogen induction of PRs was unaffected by deafferentation, and the total number of PR-immunoreactive neurons was similar in the control, deafferented and contralateral VMNvl. The results show that estrogens enhance synaptogenesis in the VMNvl by acting through neural afferents and induce PR expression by acting directly upon VMN neurons.
雌激素对下丘脑腹内侧核腹外侧部（VMNvl）的影响对于其在调节雌性性行为中的作用至关重要。增强突触形成和孕激素受体（PRs）的诱导是雌激素对 VMNvl 作用的标志。为了研究神经传入在介导这些效应中的影响，我们在单侧 VMN 去传入后，估计了去传入和对侧 VMNvl 以及未手术大鼠（对照）中每个神经元的棘突和树突突触数以及 PR 免疫反应性神经元的总数。在去传入的 VMNvl 中，雌激素的给药并没有引起去传入 VMNvl 中突触数的任何增加。在对侧 VMNvl 中，雌激素的促突触形成作用很明显，但仍低于对照 VMNvl，其中在雌激素刺激后观察到总突触数增加了 25%。在没有雌激素刺激的情况下，即基础条件下，去传入减少了树突和棘突突触的数量，但后者尤其明显。在对侧 VMNvl 中也可以看到这种减少，但不那么明显。与突触不同，PR 的雌激素诱导不受去传入的影响，并且在对照、去传入和对侧 VMNvl 中 PR 免疫反应性神经元的总数相似。结果表明，雌激素通过作用于神经传入来增强 VMNvl 中的突触形成，并通过直接作用于 VMN 神经元来诱导 PR 表达。
