What about the love molecule?

Following up on chemical messengers used by the brain and their modulators, today I will talk about oxytocin, the “love molecule”.

Oxytocin is a neuromodulator, that is, as I already written on my previous post about serotonin, a molecule able to modulate the transmission of information among neurons. However, oxytocin is also a hormone (basically, a substance produced in an organism and transported in tissue fluids, such as blood, to stimulate specific cells or tissues into action). This double identity of oxytocin is due to its multiple pathways of release: it is produced by neurons in the posterior lobe of the pituitary gland, a pea-sized structure at the base of the brain called hypothalamus, and from there is released in the bloodstream and in the cerebrospinal fluid, but it also reaches neural targets in the brain through direct projections (see picture below).

Schematic of the oxytocin production site and a brief overview of its multiple pathways of diffusion.
Modified from

It is known that oxytocin regulates social interaction and sexual reproduction, since it plays a role in behaviours like maternal-infant bonding and milk release, but also empathy, generosity and social relationships. Researches show that the levels of oxytocin increase during hugging, orgasm or even petting a dog: consequently, as a result, oxytocin is commonly referred to as the “love hormone”.

Usually, females have higher levels than males and oxytocin is prescribed as a drug for obstetric and gynaecological reasons and can help in childbirth, since it causes uterine contractions during labor and it helps shrink the uterus after delivery. Moreover, when an infant suckles at his or her mother’s breast, the stimulation causes a release of oxytocin, which, in turn, tells the body to “release” milk for the baby to drink.

Oxytocin also increases pro-social behaviours like altruism, generosity and empathy, leading to a predisposition into trusting other people. Experimental results show that intranasal administration of oxytocin makes people more prone to help others and better into recognising emotions. It is believed that these socio-cognitive effects are due to a suppression of the prefrontal and cortico-limbic circuits, that in turn leads to a reduction in social restraints and emotions like fear, anxiety and stress. Due to these effects on social behaviours and other researches, it is believed that oxytocin may also help as a treatment for a number of conditions, including depression and anxiety, as well as people with an autistic spectrum disorder (ASD) and irritable bowel syndrome (IBS), due to its action on intestinal problems.

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