Pulsatile release of oxytocin in newborn infants

Recently, a pulsatile, basal oxytocin blood level has been described in human adults. To investigate if such a hormone profile exists already during the neonatal period, we collected blood samples continuously with 20-s fractions for 4 min in 1-day-old infants (n = 26). Plasma oxytocin concentrations were determined by a specific radioimmunoassay. The values were further analysed by the pulse detection program PULSAR. We found that 42% of the infants presented one peak in the oxytocin level during a 4-min period. The peak constituted a 111 +/- 66% (mean +/- SD) increment of the baseline value. It is suggested that the release of oxytocin during basal conditions occurs in a pulsatile way in newborn infants and that these hormone pulses reflect fluctuations in the activity of the hypothalamic neurosecretory cells.