Oxytocin

Oxytocin is a nonapeptide hormone that has a central role in the regulation of parturition and lactation. ^[1] It is a peptide hormone secreted from the pituitary that is also released in the brain, where it acts as a neuromodulator to shape several aspects of social behavior. ^[2]

The oxytocin receptor belongs to the rhodopsin-type (Class 1) G-protein coupled receptor superfamily, and receptor activation in the myometrium triggers signalling events that stimulate contraction primarily by elevating intracellular calcium. ^[1] In the brain, oxytocin can enhance the salience of social stimuli and increase signal-to-noise ratios by modulating spiking and synaptic plasticity within circuits and networks. ^[3] Oxytocin regulates the salience of social cues through its interaction with the dopaminergic system, and its effects depend on context and on individual differences such as gender, personality traits, and degree of psychopathology, so it can induce antisocial effects including aggression and envy. ^[4]

The current World Health Organization recommendation for preventing postpartum haemorrhage is 10 international units of intramuscular or intravenous oxytocin, and a network meta-analysis found oxytocin effective for preventing postpartum haemorrhage. ^[5] In a network meta-analysis of drug therapy for frontotemporal dementia, high-dose oxytocin (72 international units) was associated with the greatest improvement in patients' neuropsychiatric symptoms compared with placebo. ^[6] In a network meta-analysis of treatments for autism spectrum disorder, oxytocin improved repetitive behaviors in adults with moderate confidence, though routine prescription of medications for the core symptoms could not be recommended. ^[7] Experimental rodent and non-human primate data link oxytocin to behavior and physiology fairly consistently, but human data are largely correlative and inconclusive, in part because the pulsatile release and short half-life of plasma oxytocin limit the validity of single plasma assessments. ^[8]

As women transition into menopause, oxytocin levels decrease while their susceptibility to mood disorders, poor sleep, osteoporosis, and cardiovascular diseases increases, highlighting oxytocin as a potential influence on the health and mood of women across the reproductive life span. ^[8] Oxytocin is anti-inflammatory and is associated with recently evolved social solutions to challenges of mammalian survival, with implications for health and longevity including the prevention and treatment of excess inflammation and related disorders. ^[9] In preclinical work the entire oxytocin system is synthesized in the rat and human heart, where oxytocin treatment attenuates cardiomyocyte death from ischemia-reperfusion and reduces cardiac apoptosis, fibrosis, and hypertrophy. ^[10]