Egli Marcel, Bertram Richard, Sellix Michael T, Freeman Marc E
Department of Biological Sciecne, Florida State University, Tallahassee, Florida 32306-4340, USA.
Endocrinology. 2004 Jul;145(7):3386-94. doi: 10.1210/en.2003-1710. Epub 2004 Mar 19.
Prolactin (PRL) is secreted from lactotrophs of the anterior pituitary gland of rats in a unique pattern in response to uterine cervical stimulation (CS) during mating. Surges of PRL secretion occur in response to relief from hypothalamic dopaminergic inhibition and stimulation by hypothalamic releasing neurohormones. In this study, we characterized the role of oxytocin (OT) in this system and the involvement of vasoactive intestinal polypeptide (VIP) from the suprachiasmatic nucleus (SCN) in controlling OT and PRL secretion of CS rats. The effect of OT on PRL secretion was demonstrated in cultured lactotrophs showing simultaneous enhanced secretion rate and increased intracellular Ca(2+). Neurosecretory OT cells of the hypothalamic paraventricular nucleus that express VIP receptors were identified by using immunocytochemical techniques in combination with the retrogradely transported neuronal tracer Fluoro-Gold (iv injected). OT measurements of serial blood samples obtained from ovariectomized (OVX) CS rats displayed a prominent increase at the time of the afternoon PRL peak. The injection of VIP antisense oligonucleotides into the SCN abolished the afternoon increase of OT and PRL in CS-OVX animals. These findings suggest that VIP from the SCN contributes to the regulation of OT and PRL secretion in CS rats. We propose that in CS rats the regulatory mechanism(s) for PRL secretion comprise coordinated action of neuroendocrine dopaminergic and OT cells, both governed by the daily rhythm of VIP-ergic output from the SCN. This hypothesis is illustrated with a mathematical model.
催乳素（PRL）由大鼠垂体前叶的催乳细胞以独特模式分泌，以响应交配期间子宫颈刺激（CS）。催乳素分泌激增是对下丘脑多巴胺能抑制解除以及下丘脑释放神经激素刺激的反应。在本研究中，我们确定了催产素（OT）在该系统中的作用，以及来自视交叉上核（SCN）的血管活性肠肽（VIP）在控制CS大鼠OT和PRL分泌中的作用。在培养的催乳细胞中证实了OT对PRL分泌的影响，表现为分泌速率同时提高和细胞内Ca（2+）增加。通过免疫细胞化学技术结合逆行转运的神经元示踪剂荧光金（静脉注射），鉴定了下丘脑室旁核中表达VIP受体的神经分泌OT细胞。从去卵巢（OVX）CS大鼠获得的系列血样的OT测量显示，在下午PRL峰值时显著增加。向SCN注射VIP反义寡核苷酸消除了CS-OVX动物中OT和PRL的下午增加。这些发现表明，来自SCN的VIP有助于调节CS大鼠的OT和PRL分泌。我们提出，在CS大鼠中，PRL分泌的调节机制包括神经内分泌多巴胺能和OT细胞的协同作用，两者均受SCN中VIP能输出的昼夜节律控制。用数学模型说明了这一假设。
