oxytocin

Hormone that stimulates the uterus in late pregnancy to initiate and sustain labour. It is secreted by the pituitary gland. After birth, it stimulates the uterine muscles to contract, reducing bleeding at the site where the placenta was attached.

Intravenous injections of oxytocin may be given to induce labour, strengthen contractions, or control haemorrhage after birth. It is also secreted during lactation. Oxytocin sprayed in the nose a few minutes before nursing improves milk production.

The hormone is released in mammals at the beginning of relationships, including mating as well as at birth, meaning it helps to form other relationships as well as maternal bonding. In 2000 US researchers established the function oxytocin plays in relationships by using male mice genetically engineered to lack the hormone. They discovered these mice retained no memory of female mice previously encountered and so believe that oxytocin is vital in ‘social memory’. The mice that were deprived of oxytocin showed no other signs of any memory impairment.