Helou Ammir Y, de Carvalho Camila, do Carmo Larissa A, Bittencourt Jackson C
Laboratory of Chemical Neuroanatomy, Department of Anatomy, Institute of Biomedical Sciences, University of Sao Paulo, Sao Paulo, SP, Brazil.
Center for Neuroscience and Behavior, Institute of Psychology, University of Sao Paulo, Sao Paulo, SP, Brazil.
J Neuroendocrinol. 2025 Aug;37(8):e70043. doi: 10.1111/jne.70043. Epub 2025 May 14.
This study examines the influence of litter sex composition on melanin-concentrating hormone immunoreactive (MCH-ir) neurons in the ventromedial medial preoptic area (vmMPOA) and on plasma prolactin levels in lactating rats. MCH is a critical regulator of maternal behavior and displays sexual dimorphism within the MPOA, making it an important target for understanding neuroendocrine adaptations in lactation. Prolactin, a pivotal hormone in lactation and maternal care, was also assessed to elucidate its interaction with litter sex composition. Thirty lactating female rats were divided into five experimental groups based on litter sex composition: all-male (10 male pups), all-female (10 female pups), balanced control (five male and five female pups), predominantly male (seven male and three female pups), and predominantly female (three male and seven female pups). On post-partum day 19 (PPD19), the dams were euthanized for biological analysis. Blood samples were collected for plasma prolactin quantification, and the brains were processed to analyze MCH-ir neurons in the vmMPOA. Results showed no significant differences in food and water intake or the number of MCH-ir neurons in the vmMPOA among experimental groups. However, significant variation in prolactin levels was observed, with the all-male offspring group exhibiting the highest levels (mean prolactin level 23.9 ng/mL, p < .001), followed by the all-female group (20.3 ng/mL, p < .01), compared to the control group (14.3 ng/mL). Additionally, the all-male group showed a reduction in body weight gain. These results suggest that although litter sex composition does not alter the number of MCH-ir neurons in the vmMPOA, it significantly impacts maternal prolactin levels. This differential prolactin regulation may reflect distinct physiological demands or caregiving behaviors imposed by homogeneous litters, which could, in turn, influence maternal energy balance, lactation efficiency, and adaptive maternal responses. Understanding these sex-specific influences on maternal neuroendocrine function has important implications for comprehending maternal care dynamics and energy allocation during lactation.
本研究考察了窝仔性别组成对泌乳大鼠腹内侧视前区（vmMPOA）中黑色素聚集激素免疫反应性（MCH-ir）神经元以及血浆催乳素水平的影响。MCH是母性行为的关键调节因子，且在视前区呈现出性别二态性，这使其成为理解泌乳期神经内分泌适应性的重要靶点。催乳素是泌乳和母性照料中的关键激素，本研究也对其进行了评估，以阐明其与窝仔性别组成的相互作用。30只泌乳雌性大鼠根据窝仔性别组成被分为五个实验组：全雄组（10只雄性幼崽）、全雌组（10只雌性幼崽）、平衡对照组（5只雄性和5只雌性幼崽）、雄性为主组（7只雄性和3只雌性幼崽）以及雌性为主组（3只雄性和7只雌性幼崽）。在产后第19天（PPD19），对母鼠实施安乐死以进行生物学分析。采集血样用于血浆催乳素定量分析，并对大脑进行处理以分析vmMPOA中的MCH-ir神经元。结果显示，各实验组之间在食物和水摄入量或vmMPOA中MCH-ir神经元数量上无显著差异。然而，观察到催乳素水平存在显著差异，全雄后代组的催乳素水平最高（平均催乳素水平为23.9 ng/mL，p <.001），其次是全雌组（20.3 ng/mL，p <.01），而对照组为（14.3 ng/mL）。此外，全雄组的体重增加有所减少。这些结果表明，尽管窝仔性别组成不会改变vmMPOA中MCH-ir神经元的数量，但它会显著影响母鼠的催乳素水平。这种催乳素调节的差异可能反映了同质性窝仔所施加的不同生理需求或照料行为，这反过来可能会影响母鼠的能量平衡、泌乳效率和适应性母性反应。了解这些对母性神经内分泌功能的性别特异性影响对于理解泌乳期的母性照料动态和能量分配具有重要意义。
