Oxytocin is a neuropeptide that was discovered between 1909 and 1911 by Sir Henry Hallett Dale. (Nobel Foundation. 1936 Laureates) (Dale was a recipient of the 1936 Nobel Prize in Physiology or Medicine for his contributions to early neuroscience including the identification of acetylcholine, his views on chemical neural signaling and his now semi-disproved Dale’s Principle which states a neuron could only specialize in one type of neurotransmitter.)
Like other peptide neurotranmitters, Oxytocin is produced from larger protein precursors called polyproteins or prohormones. (Kandel, Schwartz, and Hessell. 288-289.)
In the nervous system, the presence of oxytocin increases Na++ secretion. In the mammary glands, oxytocin causes the contraction of smooth muscles, leading to milk ejection. It is believed that Oxytocin is stimulated by olfactory cues. (Purves, Augustine, Fitzpatrick, Katz et al. Ch 30)
Oxytocin also causes the myometrial muscle smooth muscle to contract. (which are aided by prostaglandins) (Hill, Wise and Anderson. 442)
In the Prairie Vole, oxytocin is released into the brain of the female during mating. This is attributed with the formation of a monogamous pair bond with her partner. In the related mountain vole, oxytocin is not released during mating and the mountain vole leads a promisquous lifestyle.
In humans, plasma concentrations of oxytocin have been reported to be higher amongst people who claim to be falling in love. Oxytocin has a role in social behaviors in many species, and so it seems likely that it has similar roles in humans. It has been suggested that deficiencies in oxytocin pathways in the brain might be a feature of autism.
There has been some evidence to suggest that Oxytocin may have been involved in Obsessive Compulsive Disorder or a similar disorder. However, double blind studies have not been able to provide statistically viable data to support this hypothesis.
Disorders wherein levels are elevated or lowered
Excess oxytocin has no known significant problems. A lack of oxytocin may result in a decrease in milk ejection during lactation. (Lapping-Carr)
