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Oxytocin

Oxytocin (CAS 50-56-6) is a cyclic nonapeptide hormone (Cys-Tyr-Ile-Gln-Asn-Cys-Pro-Leu-Gly-NH₂) with a molecular weight of approximately 1,007.2 Da, synthesized in the paraventricular and supraoptic nuclei of the hypothalamus and released from the posterior pituitary. The structure features an intramolecular disulfide bond (Cys¹-Cys⁶) forming a 20-membered ring with a three-residue C-terminal tail. Oxytocin is a premier research tool in social neuroscience, reproductive biology, and GPCR signaling, acting through the oxytocin receptor (OXTR).

Technical Specifications

Property Value
CAS Number 50-56-6
Molecular Formula C₄₃H₆₆N₁₂O₁₂S₂
Molecular Weight ~1,007.2 Da
Purity ≥98% (HPLC-verified)
Appearance Lyophilized white powder
Solubility Soluble in sterile water and aqueous buffers
Storage -20°C (lyophilized), 2–8°C (reconstituted)

Mechanism of Action

Oxytocin exerts its effects through the oxytocin receptor (OXTR), a Gαq/11-coupled GPCR expressed in the uterus, mammary myoepithelium, and throughout the central nervous system (amygdala, hippocampus, nucleus accumbens, prefrontal cortex). OXTR activation triggers PLC-mediated IP₃ production and intracellular calcium mobilization, leading to calcium/calmodulin-dependent myosin light chain kinase (MLCK) activation in smooth muscle — this drives uterine contraction during parturition and milk ejection from mammary tissue. In the CNS, OXTR coupling to Gαq and Gαi/o pathways modulates neuronal excitability: in the amygdala, oxytocin reduces fear responses by enhancing GABAergic interneuron activity in the central amygdala; in the nucleus accumbens and prefrontal cortex, it facilitates social reward processing, pair-bond formation, and trust behavior through dopaminergic pathway modulation. Oxytocin also demonstrates remarkable structural similarity to vasopressin (differing by only 2 of 9 residues: Ile³→Phe and Leu⁸→Arg), and both hormones exhibit moderate cross-reactivity at each other's receptors (OTR, V1aR, V1bR, V2R), a feature essential for dose-response interpretation in research protocols.

Research Applications

  • Primary: Social neuroscience — pair bonding, social cognition, trust and affiliation behavior
  • Secondary: Reproductive physiology (uterine contractility, lactation), stress and anxiety neurobiology, autism spectrum disorder models
  • Model Systems: In vitro (OXTR-transfected cell lines, myometrial strip contractility assays), in vivo (social behavior paradigms in rodents and voles, maternal behavior studies, intranasal administration pharmacokinetics)

Quality Control & Analytical Methods

  • HPLC: ≥98% purity verification at 214/220 nm (C18 reversed-phase column)
  • Mass Spectrometry: ESI-MS for molecular weight confirmation (~1,007.2 Da)
  • Peptide Content: Amino acid analysis (AAA) for net peptide content determination
  • Endotoxin: <1 EU/mg (LAL assay)
  • TFA Content: <1% (ion chromatography)

Stability & Storage

Condition Stability
-20°C (lyophilized) 24 months
4°C (lyophilized) 6 months
25°C (lyophilized) 1 month
Reconstituted (4°C) 7 days
Reconstituted (-20°C) 30 days

Key Research References

  • Donaldson & Young (2008) — Oxytocin, vasopressin, and the neurogenetics of sociality. Science. PMID: 19001180
  • Gimpl & Fahrenholz (2001) — The oxytocin receptor system: structure, function, and regulation. Physiol Rev. PMID: 11274341
  • Meyer-Lindenberg et al. (2011) — Oxytocin and vasopressin in the human brain: social neuropeptides for translational medicine. Nat Rev Neurosci. PMID: 21730846

Source & Purchase

For researchers requiring research-grade OXYTOCIN with full analytical documentation including HPLC, LC-MS, and Certificate of Analysis, visit the HK Peptides product page for specifications, bulk pricing, and ordering.

View OXYTOCIN Product →

FAQ

Q: What purity level is standard for Oxytocin? A: HK Peptides supplies Oxytocin at ≥98% purity by HPLC with full COA documentation.

Q: How should Oxytocin be stored for research use? A: Lyophilized Oxytocin should be stored at -20°C. Reconstituted solutions at 4°C for short-term use (up to 7 days). Avoid repeated freeze-thaw cycles.