Sutherland R C, Aizlewood E S, Wakerley J B
J Reprod Fertil. 1986 Jan;76(1):123-30. doi: 10.1530/jrf.0.0760123.
The pattern of reflex milk ejection during suckling was investigated in anaesthetized Wistar rats at various stages of pregnancy, lactation and after weaning. Milk-ejection responses were measured using intramammary pressure recordings, and the amount of oxytocin released was estimated from log dose-response lines compiled from the mammary responses to exogenous oxytocin. The number of rats showing intramammary pressure responses to oxytocin increased on Day 22 of pregnancy (the day of parturition) and decreased at 8 days after weaning. The dose-response lines from pregnant animals were shallow, but steepened and shifted to the left during lactation and after weaning. Reflex milk-ejection responses during suckling were detectable in primigravid animals, indicating that birth of the litter and previous suckling experience are unnecessary for the immediate functioning of the reflex. Reflex milk-ejection responses improved during early lactation (such that the frequency and the amount of oxytocin released at each response were maximal at Day 10 of lactation), and subsequently declined in late lactation. Although the frequency of responses in animals 2 and 4 days after weaning was similar to that in late lactating animals, the amount of oxytocin released at each response had risen again to mid-lactation values. In animals undergoing a second pregnancy and lactation the pattern of change in the milk-ejection responses was similar to that of primiparous animals.
在麻醉状态下，对处于妊娠、哺乳各阶段及断奶后的Wistar大鼠在哺乳期间的反射性排乳模式进行了研究。使用乳腺内压力记录来测量排乳反应，并根据由乳腺对外源催产素的反应所编制的对数剂量反应曲线来估算催产素的释放量。对催产素出现乳腺内压力反应的大鼠数量在妊娠第22天（分娩日）增加，在断奶后8天减少。妊娠动物的剂量反应曲线较平缓，但在哺乳期间及断奶后变陡并向左移动。初孕动物在哺乳期间可检测到反射性排乳反应，这表明产仔和先前的哺乳经历对于该反射的即时运作并非必要。反射性排乳反应在哺乳早期有所改善（以至于在哺乳第10天，每次反应时催产素释放的频率和量达到最大值），随后在哺乳后期下降。虽然断奶后2天和4天的动物反应频率与哺乳后期动物相似，但每次反应时催产素的释放量再次上升至哺乳中期水平。在经历第二次妊娠和哺乳的动物中，排乳反应的变化模式与初产动物相似。
