Karyakin M G, Alekseev N P
Institute of Physiology, St. Petersburg State University, Russia.
J Comp Physiol A. 1992 Jun;170(5):645-50. doi: 10.1007/BF00199340.
Changes of positive pressure exerted by pups on nipples during sucking were investigated using anesthetized, lactating dams. It was found that, every 50-60 s, individual pups performed bouts of pressure oscillations (3/s) of high amplitude which lasted about 10-12 s and coincided with periods of increased motor activity. During the intervals, when pups were quiet, series of low-amplitude oscillations (3/s) were also observed. Using a strain measuring method to record the activity of sucking pups, synchronization of activity of two or more pups was found to occur periodically every 25-30 s and, most frequently, 10-30 s before the reflex increase of milk pressure. In further experiments, artificial tactile stimulation was applied to the dam's nipples using the joint action of suction and positive pressure. Following a short-term (10-20 s) increase in frequency and amplitude of artificial nipple stimulation, 60%-80% of all reflexive peaks of milk pressure were elicited with a latency of 19 +/- 5 s. This suggests that there are specific conditions under which the stimulation of nipples by pups may trigger the formation of the milk ejection reflex in the rat.
利用麻醉的泌乳母鼠，研究了幼崽在吸吮过程中对乳头施加的正压变化。结果发现，每隔50 - 60秒，单个幼崽会进行一系列高振幅的压力振荡（3次/秒），持续约10 - 12秒，且与运动活动增加的时期一致。在幼崽安静的间隔期间，也观察到一系列低振幅振荡（3次/秒）。使用应变测量方法记录吸吮幼崽的活动，发现两个或更多幼崽的活动每隔25 - 30秒周期性同步，且最常发生在乳汁压力反射性增加前10 - 30秒。在进一步的实验中，利用吸力和正压的联合作用对母鼠乳头进行人工触觉刺激。在人工乳头刺激的频率和振幅短期（10 - 20秒）增加后，60% - 80%的所有乳汁压力反射峰值被诱发，潜伏期为19±5秒。这表明在特定条件下，幼崽对乳头的刺激可能会触发大鼠乳汁喷射反射的形成。
