Higuchi T, Uchide K, Honda K, Negoro H
Exp Neurol. 1987 May;96(2):443-55. doi: 10.1016/0014-4886(87)90061-6.
To clarify the origin of dystocia in bilaterally pelvic neurectomized (BPN) rats, the uterine activity during the periparturient period, and reflex straining movements in response to vaginal stimulation and cervical extensibility were monitored. The BPN rat displayed "stretching" movements and the regular continuous uterine activity with a similar onset and intensity to that in control rats (intact, sham-operated or unilateral pelvic neurectomized rats) on days 22 or 23 of gestation, but lacked the "straining" movements which precede each delivery of pups in controls so that parturition was prolonged. Dissection of rats revealed that an unborn fetus was retained in the expanded upper portion of the vaginal cavity. Vaginal distension induced contraction of the abdominal muscles and diaphragm and an inhibition of respiratory movements, resulting in an increase in intraabdominal pressure in urethane-anesthetized control rats. This reflex muscular contraction which reflects the straining movements in normal delivery may be called the fetus-expulsion reflex and does not occur in BPN rats. It differs from the fetus-ejection reflex (Ferguson reflex) which initiates oxytocin release. There was no difference in weight and distensibility of the uterine cervix between sham-operated and operated rats on day 22 of pregnancy. The results suggest that the main abnormality of delivery in BPN rats, a prolongation of the process of delivery, may be due to a lack of the fetus-expulsion reflex which plays a physiologic role in removing a fetus from the upper vaginal cavity against the resistance of the pelvic outlet.
为了阐明双侧盆腔神经切除（BPN）大鼠难产的原因，对围产期子宫活动、阴道刺激引起的反射性努责运动以及宫颈伸展性进行了监测。在妊娠第22或23天，BPN大鼠表现出“伸展”运动和规律的持续性子宫活动，其起始和强度与对照大鼠（完整、假手术或单侧盆腔神经切除大鼠）相似，但缺乏对照大鼠每次分娩幼崽前的“努责”运动，因此分娩时间延长。解剖大鼠发现，一个未出生的胎儿滞留在扩张的阴道腔上部。阴道扩张可引起腹肌和膈肌收缩以及呼吸运动抑制，导致氨基甲酸乙酯麻醉的对照大鼠腹腔内压力升高。这种反映正常分娩时努责运动的反射性肌肉收缩可能被称为胎儿排出反射，而在BPN大鼠中不发生。它与引发催产素释放的胎儿娩出反射（弗格森反射）不同。在妊娠第22天，假手术大鼠和手术大鼠的子宫颈重量和伸展性没有差异。结果表明，BPN大鼠分娩的主要异常，即分娩过程延长，可能是由于缺乏胎儿排出反射，该反射在克服骨盆出口阻力将胎儿从阴道上部腔隙排出过程中发挥生理作用。
