Herbison A E, Voisin D L, Douglas A J, Chapman C
Laboratory of Neuroendocrinology, Babraham Institute, Cambridge, United Kingdom.
Endocrinology. 1997 Jan;138(1):33-40. doi: 10.1210/endo.138.1.4859.
The magnocellular oxytocin neurons of the hypothalamic supraoptic (SON) and paraventricular nuclei play an important role in the initiation and maintenance of parturition in the rat. As little is known about the neural inputs responsible for activating oxytocin neuron activity at this time, we used the technique of microdialysis to examine the profile of monoamine and excitatory amino acid neurotransmitter release within the SON before and during parturition. Microdialysis probes were implanted into the SON of anesthetized pregnant rats (n = 8) on the morning of the day preceding parturition (day 20), and 15-min dialysate samples were collected from freely moving animals over the following 2 days until 3 h after birth of the last pup. On the day of parturition (day 21), dialysate concentrations of norepinephrine were significantly increased (P < 0.05) in the hour leading up to the expulsion of the first pup and, compared with those on the previous day, remained at significantly (P < 0.05) elevated levels throughout the course of parturition. A significant (P < 0.01) increase in glutamate concentrations was also detected, although in this case, it was only elevated transiently in the 15-min period immediately before the onset of pup expulsion. Mean levels of dopamine were not different between days 20 and 21, but a significant increase in dopamine release was detected specifically during the second half of parturition. No significant changes in serotonin and aspartate concentrations were observed on days 20 and 21 or in relation to parturition. This study provides an analysis of neurotransmitter release in the SON over parturition and indicates that norepinephrine concentrations are elevated well in advance of the onset of pup expulsion, whereas a burst of glutamate release occurs immediately before the birth of the first pup. Such changes are likely to reflect activity in afferent inputs to the SON and may represent neurochemical events involved in the initiation and maintenance of parturition.
下丘脑视上核（SON）和室旁核的大细胞催产素神经元在大鼠分娩的启动和维持过程中发挥着重要作用。由于目前对负责激活催产素神经元活动的神经输入了解甚少，我们采用微透析技术来检测分娩前和分娩期间SON内单胺和兴奋性氨基酸神经递质的释放情况。在分娩前一天（第20天）的早晨，将微透析探针植入麻醉的怀孕大鼠（n = 8）的SON中，并在接下来的2天内从自由活动的动物身上收集15分钟的透析液样本，直到最后一只幼崽出生后3小时。在分娩当天（第21天），在排出第一只幼崽前的1小时内，去甲肾上腺素的透析液浓度显著升高（P < 0.05），并且与前一天相比，在整个分娩过程中一直保持在显著升高（P < 0.05）的水平。还检测到谷氨酸浓度显著（P < 0.01）升高，不过在这种情况下，仅在幼崽排出开始前的15分钟内短暂升高。第20天和第21天多巴胺的平均水平没有差异，但在分娩后半期检测到多巴胺释放显著增加。在第20天和第21天，或者与分娩相关的情况下，未观察到血清素和天冬氨酸浓度有显著变化。这项研究分析了分娩期间SON中神经递质的释放情况，表明去甲肾上腺素浓度在幼崽排出开始前就大幅升高，而在第一只幼崽出生前立即出现谷氨酸释放的爆发。这些变化可能反映了SON传入输入的活动，并且可能代表了参与分娩启动和维持的神经化学事件。
