Scientists have for the first time shown how a “trust” hormone is released in the brains of breastfeeding mothers.

It is further proof that breastfeeding promotes the maternal bond through a biochemical process.

The team at Warwick University said the hormone oxytocin was known to be released during breastfeeding but the mechanism in the brain was unclear.

Oxytocin also produces contractions during labour and causes milk to be “let down” from the mammary glands.

The hormone is produced in the hypothalamus – the part of the brain that controls body temperature, thirst, hunger, anger and tiredness.

It has been shown to promote feelings of trust and confidence and to reduce fear.

Co-ordination

The study, published in the journal PLoS Computational Biology, found that in response to a baby suckling, specialised neurons in the mothers’ brain start to release the hormone from the nerve endings.

But surprisingly oxytocin is also released from the part of the cell called the dendrite which is usually the part of a neurone which receives, rather than transmits information.

Using a mathematical model, the researchers worked out that this release from the dendrites allows a massive increase in communication between the neurons, co-ordinating a “swarm” of oxytocin factories producing intense bursts of the hormone.

They is an example of an “emergent process”, the scientists said – a closely co-ordinated action developing without a single leader, in the same as a flock of birds or insects swarms.

Study leader, Professor Jianfeng Feng said: “We knew that these pulses arise because, during suckling, oxytocin neurons fire together in dramatic synchronised bursts.

“But exactly how these bursts arise has been a major problem that has until now eluded explanation.

“The model gives us a possible explanation of an important event in the brain that could be used to study and explain many other similar brain activities.”

A spokesperson for the National Childbirth Trust (NCT) said breastfeeding for up to two years can have “significant health benefits” for mother and baby.