Oxytocin

Oxytocin Peptide

Oxytocin is a naturally occurring cyclic peptide hormone composed of nine amino acids. Scientists consider the peptide hormone to be secreted by the pituitary gland and to act as a neurotransmitter within the brain.⁽¹⁾ The synthetic form of the peptide, Recombinant Oxytocin, is a cyclic nonapeptide developed to be analogous to the naturally occurring peptide.⁽²⁾

The first isolation of the peptide was carried out in 1920, followed by its structure discovery in the 1950s. Several research studies were conducted to fully explore the peptide’s action and characteristics. Scientists consider it to be created by the hypothalamus, and Oxytocin is then secreted and stored in the posterior pituitary gland, potentially released in the event of a specific stimulation.⁽³⁾ Unlike other hormones, naturally occurring Oxytocin has been posited to work via a positive feedback mechanism. This means that the initial secretion of the hormone peptide may lead to further release of the peptide in higher concentrations and with higher intensity.⁽³⁾ Both synthetic and natural forms appear to work through the same potential mechanisms.

Considered to be especially pivotal in the process of gestation and labor, Oxytocin, once secreted into the system, may bind with the G-protein coupled receptors to potentially increase intracellular calcium levels. This calcium secretion may have various downstream impacts, such as inducing uterine contractions. Once the uterine contractions begin, they may stimulate further release of Oxytocin, leading to higher frequency and intensity of the contractions via a positive feedback mechanism.⁽³⁾ The peptide appears to contribute to the contractions of myoepithelial cells found in the alveolar ducts of mammary glands. These contractions may stimulate milk ejection from alveolar ducts into the larger sinuses, thereby expelling milk. The positive feedback mechanism may also work here, with initial milk expulsion potentially stimulating increased Oxytocin circulation and continuous milk release.⁽³⁾

Chemical Makeup

Molecular Formula: C₄₃H₆₆N₁₂O₁₂S₂
Molecular Weight: 1007.193 g/mol
Other Known Titles: endopituitrina

Research and Clinical Studies

Oxytocin Peptide and Dopamine Signaling

Oxytocin might play a role in shaping sexual behavior by possibly influencing the activity of dopamine within central nervous system regions associated with the rewards system, notably the ventral tegmental area (VTA) and the nucleus accumbens.⁽⁴⁾ This influence may stem from projections of Oxytocin to the VTA, where the peptide may either augment dopamine release, or enhance the sensitivity of dopaminergic neurons. Such an increase in dopaminergic activity may, in turn, potentially boost sexual motivation and the perception of reward, possibly aiding the anticipatory aspects of mating and copulatory behavior. The hypothesis suggests that Oxytocin may directly interact with dopaminergic neurons within the VTA by activating specific oxytocin receptors, initiating a sequence of events that culminates in heightened dopamine release within the nucleus accumbens. This sequence may include the stimulation of nitric oxide synthesis within the VTA, hinting at an intricate interplay involving Oxytocin, dopamine, and nitric oxide. Additionally, there is the potential for Oxytocin to exert an indirect action on dopaminergic activity across other cerebral locales, including the hippocampus and amygdala, adding further depth to its complex role. Such indirect influences might modulate the activity of either glutamatergic or GABAergic neurons, which may, in turn, influence dopaminergic neurons located within the VTA and nucleus accumbens.⁽⁴⁾