Like many other neuropeptides, oxytocin was known until quite recently only as a peripheral hormone, secreted from the pituitary gland. But immunocytochemistry has shown that oxytocin is present in a range of neurones and axons in the brain. These are mostly in the limbic system but also in the brain stem and spinal cord.1 Oxytocin receptors are also present on other neurones.2 Clearly oxytocin must have actions other than the familiar ones of promoting parturition and ejection of milk.

About 10 years ago it was found that infusing oxytocin into the brains of non-pregnant female rats rapidly induced maternal behaviour towards young pups.3 This was striking as treatments that attempted to mimic the supposed endocrine conditions of late pregnancy (treatment with oestrogen and progesterone, sometimes with added prolactin) had proved relatively ineffective. Similar findings have been reported in ewes, which are also hostile to offspring other …