Release of oxytocin and prolactin in response to suckling.

Abstract

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.

Physiology of milk secretion

“…In the course of lactation, levels of circulating PRL gradually decrease to return to~10 ng/mL after~6 months postpartum. PRL is episodically released in response to suckling to reach a peak in concentration in the blood 45 min after the beginning of breastfeeding, for up to 75 min in duration [63]. However, while the amount of PRL released is related to the intensity of nipple stimulation, plasma PRL concentration does not appear to be directly correlated with the volume of milk produced.…”

Mother–infant bonding and the evolution of mammalian social relationships

“…This area of the brain is involved in 'reward' and also requires the mesolimbic DA projection which detects rewarding stimuli and the ways in which they occur differently from prediction to enable 'updating' of the stimulus (Schultz & Dickinson 2000). In primates, the OT system may also be important in bonding, and in humans peripheral OT release is increased at birth, following female orgasm and exposure to neonatal images or sounds (McNeilly et al 1983;Carmichael et al 1987). The mother-infant bonding process entails obsessive grooming, especially to hands, face and genitalia, by mothers, and these are the morphological traits of infant monkeys that show the greatest changes during development.…”

Post-weaning breast milk HIV-1 viral load, blood prolactin levels and breast milk volume

“…It has been shown to increase significantly in response to the stimulus of breastfeeding [26][27][28][29], diminish with the onset of non-exclusive breastfeeding [30] and fall precipitously after suckling has ended [31]. Hyperprolactinemia is also known to occur in up to one-fifth of HIVinfected non-lactating individuals [32,33] but has not been assessed in lactating HIV-infected women.…”