Under the microscope: Oxytocin
Dr. Phyllis Zelkowitz’s CIHR Team in Perinatal Mental Health at the Jewish General Hospital has produced a video, “The Science of Motherhood,” presenting their research on oxytocin, as part of the Institute of Human Development, Child and Youth Health’s “IHDCYH Talks"
What is oxytocin?
Oxytocin is a natural hormone that is created in the brain. After oxytocin is created, it is released into the blood stream where it can travel to various parts of the body. Oxytocin is also created in organs outside of the brain, including the ovary, testis, and pancreas. After travelling around the body, oxytocin often binds to its receptor, which is a molecule located on the outside of cells. Once attached to its receptor, oxytocin can influence the cell to behave in a certain manner.
Researchers are extremely interested in studying oxytocin, as it is believed to be involved in various human behaviours. For example, evidence suggests that it is related to social bonding behaviours, earning it the nickname the "love hormone".
Studying oxytocin is challenging. It is released in a pulse-like fashion and remains in blood circulation for a very short period of time before it is degraded and recycled by the body. These qualities make it difficult for researchers to accurately assess circulating levels.
The primary goals of the CIHR Team in Perinatal Mental Health are to investigate perinatal levels of oxytocin, and the relationship between oxytocin and perinatal health. Here is a list of some interesting articles on oxytocin:
- Childbirth. With the onset of labour, oxytocin is increasingly released from the brain where it travels through circulation to the uterus. Arriving at the uterus, oxytocin causes muscles in the uterine wall to contract. These contractions become more frequent and stronger as labour progresses, causing the baby to move from the uterus down through the birthing canal. Studies have found that the number of oxytocin receptors (the molecules to which oxytocin binds) increase across pregnancy. At childbirth, the increase in oxytocin receptors may lead to an increase in uterine sensitivity which helps labor to progress.
- Breastfeeding. During breastfeeding, infant suckling triggers the release of oxytocin from the brain. Released oxytocin then travels through circulation to the breast, where it causes specialized cells within breast tissue to contract. The contraction of these cells forces milk stored in the breast to move down ducts or canals into the infant’s mouth.
- Maternal Behaviour. After childbirth, a special bond forms between a mother and her infant. This bond is evident in humans, as well as animals, and is important for healthy infant development. Research suggests that oxytocin may play a role in the development of this bond. Administering oxytocin to animals (e.g. mice) has been found to increase parenting behaviours, such as licking and grooming of the pups. In humans, oxytocin levels during pregnancy have been linked to maternal behaviours in the postpartum period, such as affectionate maternal touching and gazing, as well as baby talk.
- Partner Selection. The practice of choosing a mate is important in monogamous species, including humans and some animals. Interestingly, the hormone oxytocin may play a role in the formation of a monogamous relationship. Studies examining voles (rodents resembling mice) have found that the administration of oxytocin to a female’s brain increases her preference for a male vole that she has already been exposed to. Furthermore, this preference for a familiar male vole disappears when oxytocin is unable to bind to its receptor, preventing the hormone from working properly in the body. And introducing the oxytocin gene of a monogomous species into the brain of polygemous animal can make it monogamous. In humans, oxytocin levels have been found to be higher in individuals in romantic relationships compared to singles. Oxytocin levels have also been found to relate to relational behaviours, such as affectionate touching, and differentiate couples who remain together or separate several months after dating.
- Trust. Trust involves our ability to rely on another person. Our ability to trust people, even strangers, may be influenced by the hormone oxytocin. The administration of oxytocin by means of a nasal spray, to human male participants, has been shown to increase ‘trusting behaviours’, which are commonly measured in games of trust and betrayal.
- Theory of Mind. This concept refers to a person’s ability to understand the emotions and thoughts of another person. The administration of oxytocin to human male participants has been found to improve a person’s "theory of mind" capacity.
- Sexual Behaviour. Oxytocin is believed to play a role in human and animal sexual behaviours. In animals, such as rats, oxytocin is believed to be associated with lordosis (a position that females assume to assist successful mating) and copulatory behaviours (e.g. penile erection) in males. In humans, oxytocin is believed to be associated with touch (e.g. hugging) and orgasm.