O'Byrne K T, Ring J P, Summerlee A J
J Physiol. 1986 Jan;370:501-13. doi: 10.1113/jphysiol.1986.sp015947.
The extracellular electrical activity of magnocellular neurones was recorded from unanaesthetized, unrestrained rabbits in birth and the post partum suckling period. The activity of oxytocin neurones was differentiated from that of vasopressin cells on the basis of their stereotyped activity in suckling. Oxytocin neurones showed five to fourteen discrete bursts of accelerated discharge in parturition. Each burst lasted 2-22 s and represented a 3-100-fold increase in the rate of firing, compared with pre-partum values, and was followed 10-34 s later by delivery. After parturition, the spontaneous activity of these neurones returned to pre-partum rates of firing. Vasopressin neurones did not show any bursts of discharge in delivery. There was a significant fall in the discharge frequency compared with pre-partum levels (P less than 0.05: Student's t test) and a significant (P less than 0.01) lengthening of the modal interspike interval. Serial blood samples were obtained during parturition in ten rabbits. Simultaneous recordings of magnocellular neurones activity and plasma oxytocin measurements were made in four of these experiments. Plasma oxytocin profiles were related to the observed events of parturition. Frequent blood samples (0.2-0.3 ml every 10-15 s) were taken throughout delivery and plasma oxytocin measured by sensitive radioimmunoassay in unextracted plasma (lower limit sensitivity of assay 5 pg ml-1). Before birth, plasma oxytocin was 53 +/- 12 pg ml-1 (mean +/- S.E. of mean) and rose to 2846 +/- 326 pg ml-1 within 40-120 s of the onset of the expulsive phase of delivery. Peak concentrations of oxytocin were coincident with delivery of the first or second fetus. No sign of pulsatile release of oxytocin was demonstrated in the profiles but significantly (P less than 0.001) greater variance in oxytocin titres was found during birth compared with pre-partum values which is suggestive of pulsatile release. There was a straight line relationship between peak oxytocin concentrations in the plasma and the speed of delivery, implying that oxytocin facilitates as well as maintains labour in the rabbit.
在出生及产后哺乳期间，对未麻醉、未束缚的家兔记录了大细胞神经元的细胞外电活动。根据催产素神经元在哺乳时的刻板活动，将其活动与血管加压素细胞的活动区分开来。催产素神经元在分娩时显示出5至14次离散的加速放电爆发。每次爆发持续2至22秒，与产前值相比，放电速率增加了3至100倍，10至34秒后分娩。分娩后，这些神经元的自发活动恢复到产前放电速率。血管加压素神经元在分娩时未显示任何放电爆发。与产前水平相比，放电频率显著下降（P<0.05：学生t检验），且模式峰间间隔显著延长（P<0.01）。在10只家兔分娩期间采集了系列血样。其中4个实验同时记录了大细胞神经元活动和血浆催产素测量值。血浆催产素谱与观察到的分娩事件相关。在整个分娩过程中频繁采集血样（每10至15秒采集0.2至0.3毫升），并通过灵敏的放射免疫分析法在未提取血浆中测量血浆催产素（分析的下限灵敏度为5皮克/毫升）。出生前，血浆催产素为53±12皮克/毫升（平均值±平均值标准误），在分娩排出期开始后40至120秒内升至2846±326皮克/毫升。催产素的峰值浓度与第一或第二个胎儿的分娩同时出现。在谱中未显示催产素脉冲释放的迹象，但与产前值相比，出生期间催产素滴度的方差显著更大（P<0.001），这提示有脉冲释放。血浆中催产素峰值浓度与分娩速度之间存在直线关系，这意味着催产素在兔中既促进又维持分娩。
