Release of oxytocin and prolactin in response to suckling.

The oxytocin and prolactin responses to suckling were measured in 10 women in early (n = 5) and established lactation (n = 5). Oxytocin was released in a pulsatile manner during suckling in all women, but the response was not related to milk volume, prolactin response, or parity of the mother. In all 10 women plasma oxytocin concentrations increased three to 10 minutes before suckling began. In five women this occurred in response to the baby crying, in three it coincided with the baby becoming restless in expectation of the feed, while in two it corresponded with the mother preparing for the feed. There was no prolactin response to stimuli other than stimulation of the nipple associated with suckling. These results clearly indicate that the milk ejection reflex, with release of oxytocin, occurs in most women before the tactile stimulus of suckling. A second release of oxytocin follows in response to the suckling stimulus itself. Thus it is important that care is taken to protect breast feeding mothers from stress not only during suckling but also immediately before nursing, when conditioned releases of oxytocin will occur.