Breastfeeding: physiological, endocrine and behavioural adaptations caused by oxytocin and local neurogenic activity in the nipple and mammary gland.

It is now well established that oxytocin, as well as stimulating uterine contractions and milk ejection, promotes the development of maternal behaviour and also bonding between mother and offspring. In addition, oxytocin exerts by way of peripheral, circulating as well as by central, neurogenic mechanisms multiple physiological, endocrine and behavioural effects in connection with milk ejection and lactation. Some effects of oxytocin in the nipple and mammary gland appear to be exerted in close collaboration with peptides released from axon collaterals of somatosensory nerves originating in this region. The distribution of peptides localized to the somatosensory afferents in the nipple and mammary gland as well as possible effects by oxytocin and/or local neurogenic peptides in connection with milk ejection and lactation are reviewed in this paper.