Learning and mother-infant relationship based on the fetal memory in the newborn

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Mother's ventral fur, wet with amniotic fluid and ejected milk, stimulates the oral area of the newborn pup before the initial nipple grasp response in many mammals. The newborn pup receives these stimuli, probes the mother's fur, searches the nipple, and attaches it. It is hypothetized that the newborn pup memorizes characteristics of amniotic fluid, and that it associates the familiar amniotic fluid with novel stimulus, mother's milk, immediately after birth and responds to these stimuli. The aim of this study was to investigate the relationship between these stimuli and body movements in the cesarean-delivered mouse pups.The amniotic fluid obtained from pregnant females of Slc : ICR mice and mother's milk from the naturally parturient mothers were kept at 70℃ until the experiment. The fur brush was made of fur collected from around the nipple area of a donor female. Three hours after cesarean delivery each pup was tested for 9 minutes. In the baseline session, spontaneous body movements of pups were observed. In the odor presentation session, the fur brush wet with amniotic fluid, mother's milk, saline, and distilled water, was presented in front of the pup's nose. In the stimulation session, the perioral area of pups was stimulated with the brush.When the perioral area was stimulated with the fur brush and amniotic fluid, head extension and up-down movements, mouth movement, and rearlimb movement increased. Mother's milk on Day 0 had a little effect on these movements, but that on Day 3 had no specific effect. It indicates that the amniotic fluid familiar in prenatal period plays an important role for newborns to locate and attach the mother, and that the mother's milk, a novel stimulus, would be associated with the fluid and have the effect on attachment.