Oxytocin is one of the oldest and best-characterized peptide hormones in the scientific literature. It is a nonapeptide, meaning it contains nine amino acids, arranged as Cys-Tyr-Ile-Gln-Asn-Cys-Pro-Leu-Gly with an amidated C-terminus. A disulfide bond between the first and sixth residues folds the molecule into a six-residue ring with a short three-residue tail, and that shape is central to how it recognizes its receptor. The reported molecular formula is C43H66N12O12S2, with a molecular weight of about 1007.2 g/mol. Oxytocin also holds a place in the history of peptide chemistry. Vincent du Vigneaud isolated and synthesized it in the early 1950s, the first time a peptide hormone had been made in a laboratory, work that was recognized with the 1955 Nobel Prize in Chemistry.
In vivo, oxytocin is made mainly by magnocellular neurons in the hypothalamic paraventricular and supraoptic nuclei. From there it travels to the posterior pituitary for release into the circulation, and it is also released within the brain from neuronal projections. That dual role, acting as both a circulating hormone and a central neuropeptide, is one reason it appears in so many different research fields. Investigators examine how it is synthesized, processed, stored, and released, and how each of those steps is regulated in cell and tissue models.
The oxytocin receptor (OXTR) belongs to the class A family of G protein-coupled receptors. It couples mainly to Gq/11 proteins, which activate phospholipase C, generate inositol trisphosphate and diacylglycerol, and drive the release of intracellular calcium. Work in recombinant cell lines also reports coupling to other G protein families, and the signaling profile can shift with receptor density, cell type, and ligand concentration. Because oxytocin is structurally close to arginine vasopressin, it can also interact with vasopressin receptors, particularly V1a, at higher concentrations. Researchers therefore use oxytocin alongside vasopressin and synthetic analogs to map ligand selectivity and to study receptor cross-talk.
Laboratory use of oxytocin spans several areas. Receptor pharmacologists measure calcium flux, second-messenger accumulation, and receptor internalization in OXTR-expressing cell lines. Physiologists use isolated tissue preparations to study smooth muscle contractility and mammary myoepithelial cell responses in vitro. Neuroscientists study the peptide in preclinical models of social recognition, affiliative behavior, and stress-axis signaling. Each of these uses is investigational. None of them implies a benefit or a use in people, and this product is not intended for human or veterinary administration.
Oxytocin is also a convenient analytical standard. Its disulfide-bridged structure, small size, and well-documented fragmentation pattern make it useful for developing and validating HPLC and LC-MS methods, for calibrating immunoassays, and for studying how cyclic peptides behave during oxidation, reduction, and long-term storage. Groups working on peptide stability often include it as a reference when they compare formulation conditions or analytical columns.
The 5mg and 10mg vials are listed together on this page because they are the same material. Both contain the same peptide made by the same process and tested to the same standard, and the only difference is the quantity of lyophilized powder in the vial. A 5mg vial suits assay development and small, focused experiments, while the 10mg vial gives more material for longer protocols or for work shared between several researchers. Single vials and multi-vial kits are available for both sizes.
Each vial is supplied as a lyophilized powder, which helps protect the disulfide bond and the amidated terminus during storage and transport. Because the peptide contains cysteine residues, researchers usually keep it dry, cool, and protected from light and moisture until use, and follow their own institution's procedures for handling after reconstitution.
Oxytocin is also the active ingredient of prescription medicines in many countries, so it is worth being direct about what this product is. The material on this page is research-grade, is not a medicinal product, and is sold for laboratory use only. Purchasers are responsible for making sure their intended use complies with local regulations and institutional policies.
