Laboratory of Chemical Neuroanatomy, Department of Anatomy, Institute of Biomedical Sciences, University of São Paulo (USP), São Paulo, Brazil.
Department of Physiology and Biophysics, Institute of Biomedical Sciences, University of São Paulo, São Paulo, Brazil.
J Neuroendocrinol. 2019 Sep;31(9):e12723. doi: 10.1111/jne.12723. Epub 2019 May 23.
Although the melanin-concentrating hormone (MCH) and its coding mRNA are predominantly found in the tuberal hypothalamus, there is detectable synthesis of MCH in the preoptic hypothalamus exclusively in lactating dams, suggesting a participation of MCH in the alterations that take place after parturition. Also implicated in the dam physiology is oxytocin, a neurohormone released from the posterior pituitary that is necessary for milk ejection. Because the projection fields from oxytocin-immunoreactive (-IR) neurones and the mediobasal preoptic hypothalamus overlap and MCH-IR neurones are found in proximity to oxytocin neurones, we investigated the spatial relationship between MCH and oxytocin fibres. Accordingly, we employed multiple immunohistochemistry labelling for MCH and oxytocin for light and electron microscopy techniques, in addition to i.v. tracer injection combined with in situ hybridisation to identify MCH neurones that project to neurosecretory areas. As described for other strains, lactating Long-Evans dams also display immunoreactivity for MCH in the preoptic hypothalamus on days 12 and 19 of lactation. The appearance of these neurones is contemporaneous with an increase in MCH-IR fibres in both the internal layer of the median eminence and the posterior pituitary. In both regions, MCH- and oxytocin-IR fibres were found in great proximity, although there was no evidence for synaptic interaction between these two populations at the ultrastructural level. The tracer injection revealed that only mediobasal preoptic MCH neurones project to the posterior pituitary, suggesting a neuroendocrine-modulatory role for this population. When taken together, the results obtained in the present study indicate that neuroplasticity events at the mediobasal preoptic hypothalamus that occur during late lactation may be part of a neuroendocrinology control loop involving both MCH and oxytocin.
虽然黑色素浓缩激素（MCH）及其编码 mRNA 主要存在于结节下丘脑，但在哺乳期母鼠的视前下丘脑也可检测到 MCH 的合成，这表明 MCH 参与了分娩后发生的变化。在母鼠生理学中也涉及到催产素，一种从垂体后叶释放的神经激素，对于乳汁排出是必需的。由于催产素免疫反应（IR）神经元和中基底视前下丘脑的投射区域重叠，并且 MCH-IR 神经元位于催产素神经元附近，我们研究了 MCH 和催产素纤维之间的空间关系。因此，我们采用了 MCH 和催产素的多重免疫组织化学标记，用于光和电子显微镜技术，以及静脉内示踪剂注射结合原位杂交，以鉴定投射到神经分泌区域的 MCH 神经元。与其他品系描述的一样，哺乳期长耳母鼠在哺乳期第 12 和第 19 天也在视前下丘脑显示出 MCH 的免疫反应性。这些神经元的出现与正中隆起内层和垂体后叶中 MCH-IR 纤维的增加同时发生。在这两个区域，MCH-和催产素-IR 纤维非常接近，尽管在超微结构水平上没有证据表明这两个群体之间存在突触相互作用。示踪剂注射表明，只有中基底视前 MCH 神经元投射到垂体后叶，这表明该群体具有神经内分泌调节作用。综上所述，本研究获得的结果表明，在晚期哺乳期发生的中基底视前下丘脑的神经可塑性事件可能是涉及 MCH 和催产素的神经内分泌控制回路的一部分。
