title: The influence of tactile stimulation of nipples on the milk ejection reflex in the rat.
abstract: 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.
authors.affiliation: Institute of Physiology, St. Petersburg State University, Russia.
authors.forename: M G
authors.initials: MG
authors.lastname: Karyakin
authors.forename: N P
authors.initials: NP
authors.lastname: Alekseev
mesh_terms: D000818:Animals; D005260:Female; D008893:Milk Ejection / Q000502:physiology*; D009043:Motor Activity / Q000502:physiology; D009558:Nipples / Q000502:physiology*; D010812:Physical Stimulation; D011312:Pressure; D051381:Rats; D011919:Rats, Inbred Strains