Ronca A E, Alberts J R
Department of Psychology, Indiana University, Bloomington 47405, USA.
Physiol Behav. 1995 Nov;58(5):1035-41. doi: 10.1016/0031-9384(95)00155-c.
We tested the hypothesis that sensory and nonsensory factors associated with birth stimulate respiratory behavior in the fetal and newborn rat. Late gestation (Day 21) rat fetuses were externalized from the uterus with intact umbilical connections to the dam and exposed to stimuli normally associated with labor and delivery. Onset and maintenance of respiratory movements were monitored. In the first experiment, rat fetuses were exposed to either: (i) simulated uterine contractions; (ii) cooling (26 degrees C); (iii) umbilical cord occlusion; or (iv) air heated to intrauterine temperature (37.5 degrees C). Subjects were videotaped for 1 h, and respiratory movements counted during tape review. Fetuses in each group showed some respiratory behavior although compression significantly elevated respiratory rate compared to other experimental conditions. All subjects in each group were respiring after 1 h, except for pups that received umbilical cord occlusion. The 100% attrition rate of the cord occlusion-alone group was reversed by combining cord occlusion with compression, or with compression and cooling, but not by combining cord occlusion with cooling. Simulated birth pups (i.e., those exposed to compression, cooling and umbilical cord occlusion) and normal, vaginally delivered pups breathed at identical rates and showed a similar pattern of postpartum breathing. These results suggest that mechanical stimulation of the fetus associated with uterine contractions plays a critical role in the maintenance of continuous respiration at birth. Possible mechanisms for the facilitative effects of compression on perinatal breathing are discussed.
与出生相关的感觉和非感觉因素会刺激胎鼠和新生鼠的呼吸行为。妊娠晚期（第21天）的胎鼠从子宫中取出，脐带与母鼠保持完整连接，并暴露于通常与分娩相关的刺激下。监测呼吸运动的开始和维持情况。在第一个实验中，将胎鼠暴露于以下任何一种情况：（i）模拟子宫收缩；（ii）降温（26摄氏度）；（iii）脐带闭塞；或（iv）加热至子宫内温度（37.5摄氏度）的空气。对实验对象进行1小时的录像，并在查看录像时计算呼吸运动次数。尽管与其他实验条件相比，压迫显著提高了呼吸频率，但每组胎鼠都表现出了一些呼吸行为。每组中的所有实验对象在1小时后都在呼吸，除了接受脐带闭塞的幼崽。单独进行脐带闭塞的组100%的幼崽死亡，而将脐带闭塞与压迫相结合，或与压迫和降温相结合可逆转这种情况，但将脐带闭塞与降温相结合则不能。模拟出生的幼崽（即那些接受压迫、降温和脐带闭塞的幼崽）与正常经阴道分娩的幼崽呼吸频率相同，且产后呼吸模式相似。这些结果表明，与子宫收缩相关的对胎儿的机械刺激在出生时维持持续呼吸中起关键作用。文中讨论了压迫对围产期呼吸产生促进作用的可能机制。
