What role does oxytocin play in attachment?

Answer: Oxytocin is a neurohormone that signals various forms of attachment, including familial and romantic relationships.

Oxytocin is produced by the paraventricular nucleus (PVN) of the hypothalamus, a small brain structure that is important for the creation and distribution of hormones around the body. Within the PVN, there are large, neurosecretory magnocellular cells that synthesize, transport, and release oxytocin into the posterior pituitary gland for distribution.

Oxytocin acts at the oxytocin receptor (OXTR). OXTR itself is a transmembrane protein that transduces the oxytocin signal by the use of an intracellular G-protein. It belongs to the class of G-protein coupled receptors (GPCR), and signals using the Gq pathway. The OXTR is expressed peripherally in the mammary glands and the uterus. In the central nervous system, OXTR is expressed in areas such as nucleus accumbens, the amygdala, and the bed nucleus of the stria terminalis.

Peripheral action of oxytocin

Oxytocin is an important neurohormone that signals maternal care behaviors.

he milk letdown reflex is triggered by oxytocin release. In breastfeeding mothers, the suckling sensation by a newborn is transmitted by ascending spinal nerves into the hypothalamus, which induces oxytocin release. This then causes the milk to be let down to where it can be ejected.

Oxytocin is important for uterine contraction and cervical dilation when the mother is giving birth. Sometimes, the oxytocin signal that is produced during breastfeeding may cause the mother to experience uterine contractions.

Oxytocin can also pass the placenta and modulate the brain of the baby. In particular, it causes GABA to switch functions in the cortical neurons of the fetal brain, making it inhibitory. This might be done in order to protect the brain from hypoxia during birth (Maternal oxytocin triggers a transient inhibitory switch in GABA signaling in the fetal brain during delivery)

Central effects of oxytocin

The oxytocin receptor is expressed in the nucleus accumbens. It is believed that activation of oxytocin receptors in this area is responsible for mediating motherhood-like behaviors. As tested in the prairie vole animal model, it was found that elevated expression of the oxytocin receptor is associated with more motherhood like behaviors, such as grooming and hovering over the young vole. Local infusion of the oxytocin receptor antagonist d(CH2)51,Tyr(Me)2,Orn8)-AVT into the nucleus accumbens blocked the expression of motherhood behaviors (Oxytocin receptors in the nucleus accumbens facilitate “spontaneous” maternal behavior in adult female prairie voles). These data imply that normal transmission of oxytocin receptors serves a role in familial attachment.