Oxytocin 5mg

Product Overview & Disclaimer

Oxytocin is a cyclic nonapeptide hormone and neuromodulator that plays a central role in social behavior, pair bonding, maternal behavior, and reproductive physiology across mammalian species. First sequenced and synthesized in 1953 by Vincent du Vigneaud — work recognized with the 1955 Nobel Prize in Chemistry — oxytocin remains one of the most intensively studied neuropeptides in biomedical research. Oxytocin 5mg is supplied as a lyophilized (freeze-dried) powder in a sealed vial for controlled laboratory reconstitution and experimental investigation.

Quality and availability: Oxytocin 5mg is supplied at 99%+ purity and is third-party tested by an independent laboratory. Where available, Certificates of Analysis are published on our COA page. Orders ship in 2 business days. For protocols that need more material from a single vial, the same peptide is available as Oxytocin 10mg; related compounds are listed under Neuropeptide Research.

IMPORTANT NOTICE: This product is intended strictly for laboratory research and scientific investigation purposes only. It is NOT for human consumption, clinical use, diagnostic procedures, or therapeutic application of any kind. This compound has not been evaluated or approved by the FDA, EMA, or any other regulatory body for use as a drug, supplement, or medical treatment. Researchers must comply with all applicable institutional, local, state, and federal regulations governing the acquisition, handling, storage, and disposal of research peptides. BioSim Peptides assumes no liability for misuse or off-label application of this research material.

By purchasing this product, the researcher affirms that they are a qualified laboratory professional operating within an appropriately equipped research facility and that this material will be used exclusively for in vitro or approved animal model studies in accordance with institutional review protocols.

Molecular Overview

Oxytocin is a cyclic nonapeptide with the amino acid sequence Cys-Tyr-Ile-Gln-Asn-Cys-Pro-Leu-Gly-NH₂ (single-letter: CYIQNCPLG-amide). The peptide is characterized by a 20-membered disulfide ring formed between Cys¹ and Cys⁶, with a tripeptide tail (Pro-Leu-Gly-NH₂) extending from the ring. The C-terminal glycine is amidated, a post-translational modification essential for full biological activity. The molecular formula is C₄₃H₆₆N₁₂O₁₂S₂, yielding a molecular weight of approximately 1007.2 g/mol (CAS number 50-56-6).

Key physicochemical properties include:

• Hydrophobicity: Moderate amphipathic character — the disulfide-linked ring is relatively hydrophilic while the C-terminal tripeptide tail contributes hydrophobic character important for receptor binding
• Solubility: Freely soluble in water and aqueous buffers (≥10 mg/mL in water, ≥5 mg/mL in PBS pH 7.4). Limited solubility in pure organic solvents.
• Stability: The disulfide bond is susceptible to reduction by thiols and oxidation by atmospheric oxygen. Maintain reducing-agent-free conditions. Store the lyophilized powder cold and dry, protected from light.
• Extinction coefficient: ε₂₈₀ = ~1,490 M^-1cm^-1 (due to the single tyrosine residue; notably lower than many proteins)
• Structural features: The disulfide ring constrains the peptide backbone into a β-turn conformation. NMR and X-ray crystallography studies reveal that oxytocin adopts a compact, U-shaped conformation in solution with the tyrosine side chain oriented outward for receptor recognition.

Oxytocin shares remarkable structural similarity with vasopressin (Arg⁸-vasopressin), differing at only two positions: Ile³/Phe³ and Leu⁸/Arg⁸. This evolutionary relationship explains the partial cross-reactivity of both peptides at each other’s receptors — oxytocin binds the V_1a vasopressin receptor with modest affinity, and vasopressin activates the oxytocin receptor (OXTR) at high concentrations. Researchers must account for this pharmacological promiscuity when interpreting experimental results.

The oxytocin gene (OXT) is located on chromosome 20p13 in humans and encodes a preprohormone precursor (prepro-oxytocin-neurophysin I) that is processed to yield oxytocin and its carrier protein, neurophysin I. Oxytocin is synthesized primarily in magnocellular neurons of the paraventricular nucleus (PVN) and supraoptic nucleus (SON) of the hypothalamus, with axonal projections to the posterior pituitary (for peripheral hormone release) and to numerous brain regions (for central neuromodulator function).

Mechanism of Action

Oxytocin exerts its effects through a single, well-characterized G protein-coupled receptor — the oxytocin receptor (OXTR). OXTR is a class A (rhodopsin-like) GPCR encoded by the OXTR gene on chromosome 3p25.3. The receptor couples primarily to Gα_q/11 proteins, though Gα_i/o and Gα_s coupling has been reported in specific cell types and contexts, contributing to the functional diversity of oxytocin signaling.

Canonical Signaling Cascade (Gα_q/11 pathway):

1. Oxytocin binding induces conformational changes in OXTR, promoting GDP/GTP exchange on Gα_q/11.
2. Activated Gα_q/11 stimulates phospholipase C-β (PLC-β), which hydrolyzes phosphatidylinositol 4,5-bisphosphate (PIP₂) into inositol 1,4,5-trisphosphate (IP₃) and diacylglycerol (DAG).
3. IP₃ triggers Ca²⁺ release from endoplasmic reticulum stores, elevating intracellular calcium concentrations.
4. DAG activates protein kinase C (PKC), which phosphorylates downstream targets including ion channels, transcription factors, and other signaling proteins.
5. Elevated Ca²⁺ and PKC activation drive cellular responses including smooth muscle contraction (peripheral tissues), neurotransmitter release (central neurons), and gene expression changes (CREB phosphorylation).

Alternative and Context-Dependent Signaling:

• Gα_i/o coupling: In certain neuronal populations, OXTR activates pertussis toxin-sensitive G proteins, inhibiting adenylyl cyclase and reducing cAMP levels. This pathway has been studied in central amygdala circuits in rodent behavioral models.
• β-arrestin recruitment: OXTR undergoes agonist-induced phosphorylation by GRK2 (G protein-coupled receptor kinase 2), recruiting β-arrestin-1/2. This promotes receptor internalization via clathrin-coated pits and can initiate G protein-independent signaling cascades including ERK1/2 MAP kinase activation.
• Receptor dimerization: OXTR can form homodimers and heterodimers with vasopressin V_1a and V₂ receptors, modulating ligand binding affinity, signaling bias, and trafficking. Heterodimerization represents a mechanism by which oxytocin and vasopressin systems functionally interact.
• Allosteric modulation: Cholesterol and magnesium ions act as positive allosteric modulators of OXTR. Cholesterol binding sites in the receptor’s transmembrane core influence receptor conformation and ligand affinity, while Mg²⁺ enhances agonist binding affinity.

Tissue Distribution of OXTR: OXTR expression extends far beyond the classical reproductive tissues. In the central nervous system, OXTR is expressed in the amygdala, hippocampus, nucleus accumbens, prefrontal cortex, olfactory bulb, and brainstem. Peripheral expression includes uterine myometrium, mammary myoepithelium, vascular endothelium, kidney, heart, adipocytes, and pancreatic islets. This broad expression pattern underscores oxytocin’s pleiotropic physiological roles and its expanding significance across diverse research domains.

Research Applications

Oxytocin is among the most versatile and widely investigated neuropeptides in contemporary biomedical research. Its applications span an extraordinary range of disciplines:

Social Neuroscience and Behavioral Research: Oxytocin’s role as a ‘social neuromodulator’ has made it a cornerstone molecule in social neuroscience. Research models investigate oxytocin’s effects on social recognition, pair bonding, maternal behavior, trust behavior, social memory, empathy-like responses, and in-group/out-group dynamics. Prairie vole studies of pair bonding, reviewed by Insel and Young (PMID: 11252992), and the 2005 economic trust-game study by Kosfeld and colleagues (PMID: 15931222) are among the most widely cited works in this field. Current investigations explore oxytocin’s contextual and individual-difference-dependent effects, receptor polymorphisms, and epigenetic regulation of OXTR expression.

Stress Biology and HPA Axis Research: The oxytocin system is studied for its interactions with the hypothalamic-pituitary-adrenal (HPA) axis. Research models examine how oxytocin signaling relates to HPA-axis responses to acute and chronic stressors, to behavior in rodent anxiety-like and coping assays, and to amygdala and prefrontal cortex activity in response to threat-related stimuli (PMID: 16339042). The bidirectional interaction between the oxytocin system and the CRH/ACTH/cortisol cascade makes it a model for studying neuroendocrine integration.

Reproductive and Developmental Biology: The classical functions of oxytocin in parturition (uterine contraction) and lactation (milk ejection reflex) remain active areas of investigation, with contemporary research exploring the molecular regulation of OXTR expression during pregnancy, the role of local (paracrine) oxytocin production in reproductive tissues, and oxytocin’s contributions to maternal brain plasticity during the peripartum period. Developmental studies investigate oxytocin’s organizational effects on the developing brain and its role in shaping lifelong social and emotional phenotypes.

Metabolism and Energy Homeostasis: An emerging and rapidly growing research area concerns oxytocin’s metabolic effects. OXTR is expressed in adipose tissue, pancreatic islets, liver, and skeletal muscle. Published preclinical studies examine oxytocin signaling in relation to food intake, lipolysis, insulin signaling, skeletal-muscle glucose uptake and pancreatic β-cell function. This makes oxytocin a research tool for investigating neuroendocrine regulation of energy balance.

Cardiovascular and Renal Research: Oxytocin is produced in the heart and vasculature, where it acts through endothelial OXTR to stimulate nitric oxide production and promote vasodilation. Research models examine oxytocin signaling in ischemia-reperfusion, cardiac fibrosis and angiogenesis models. In the kidney, oxytocin induces natriuresis and modulates renal blood flow through effects on afferent and efferent arterioles.

Pain and Nociception: Oxytocin signaling is studied in nociception research at multiple levels of the neuraxis, including the spinal dorsal horn, periaqueductal gray, and amygdala. Research examines how oxytocin interacts with pain processing pathways and its potential interactions with endogenous opioid and cannabinoid systems.

Neuropsychiatric Research Models: The oxytocin system is studied in preclinical and observational research related to social cognition and emotional processing. OXTR gene polymorphisms, epigenetic modifications and endogenous oxytocin levels are investigated as candidate biomarkers and mechanistic variables in laboratory and animal models.

Inflammation and Immune Function: Oxytocin modulates inflammatory responses through effects on cytokine production, macrophage polarization, and T-cell differentiation. Research models investigate oxytocin signaling in inflammatory pathways and neuroimmune communication, including in stress models.

Key Research Studies

1. Kosfeld M, et al. — Economic Trust-Game Study (Nature, 2005)

This widely cited study used an economic trust-game paradigm, with a non-social risk game as a control condition, to examine the oxytocin system’s role in social decision-making. It is frequently referenced as a starting point for behavioral research on oxytocin and social cognition. PMID: 15931222

2. Kirsch P, et al. — Neural Circuitry for Social Cognition and Fear (J Neurosci, 2005)

This fMRI study examined amygdala activity and amygdala-brainstem coupling in response to fear-inducing visual stimuli, and is a key reference for research on oxytocin and the neural circuitry of social and emotional processing. PMID: 16339042

3. Meyer-Lindenberg A, et al. — Oxytocin and Vasopressin in the Human Brain (2011)

This review in Nature Reviews Neuroscience summarized neuroimaging research on oxytocin and vasopressin and the social brain network, including the amygdala, medial prefrontal cortex, anterior cingulate and nucleus accumbens. It emphasizes that findings depend on context and on individual differences, a key consideration for experimental design. PMID: 21852800

4. Guastella AJ, et al. — Encoding of Social Memories (Biol Psychiatry, 2008)

This study examined the oxytocin system’s role in social memory encoding, comparing recall of positive, negative and neutral social words, and is commonly cited in research on oxytocin and social cognition. PMID: 18343353

Additional Notable Studies:

• Ditzen B, et al. Biol Psychiatry, 2009. PMID: 19027101 — Couple-interaction study of the oxytocin system and social behavior.
• Striepens N, et al. Proc Natl Acad Sci USA, 2012. PMID: 23074247 — Highlights sex-differentiated findings and the importance of context.
• Donaldson ZR, Young LJ. Oxytocin, vasopressin, and the neurogenetics of sociality. Science, 2008. PMID: 18988842 — Review linking molecular genetics to social behavior phenotypes.
• Gimpl G, Fahrenholz F. The oxytocin receptor system: structure, function, and regulation. Physiol Rev, 2001. PMID: 11274341 — Comprehensive molecular characterization of the OXTR system.

Handling & Storage

Lyophilized Powder Storage

Oxytocin 5mg is supplied as a lyophilized powder in a sealed vial. For long-term storage, the unopened vial should be stored at -20°C in a frost-free freezer, kept dry and protected from light. The peptide’s single disulfide bond (Cys¹-Cys⁶) is the primary determinant of structural integrity — exposure to reducing agents, divalent metal ions (which catalyze disulfide rearrangement), or prolonged atmospheric oxygen can compromise the disulfide bond.

For short-term storage, sealed vials can be kept refrigerated at 2–8°C. Avoid prolonged storage at room temperature, as residual moisture can promote degradation.

Critical note on disulfide integrity: Unlike many research peptides, oxytocin requires the intact disulfide bond for receptor binding and biological activity. Reduced (linear) oxytocin has <1% of the affinity of cyclic oxytocin for OXTR. Researchers should verify disulfide bond integrity via Ellman's assay (detects free thiols) or analytical HPLC if storage conditions are uncertain.

Reconstitution Protocol

Reconstitute under aseptic conditions using sterile technique:

1. Equilibrate the sealed vial to room temperature (~15 minutes) to prevent condensation.
2. Select appropriate sterile solvent:
   • Sterile water for injection (WFI): Optimal for immediate use. Oxytocin is freely soluble at ≥10 mg/mL.
   • Sterile 0.9% saline: Compatible; oxytocin is soluble at ≥5 mg/mL.
   • Sterile PBS, pH 7.4: Recommended for maintaining physiological conditions. Solubility ≥5 mg/mL.
   • Avoid: Solutions containing reducing agents (DTT, β-mercaptoethanol, glutathione), heavy metal ions, or strong acids/bases that could reduce or scramble the disulfide bond.
3. Add the calculated volume of solvent by directing the stream onto the vial wall. Gently swirl — never vortex or sonicate, as the mechanical stress can promote oxidation and aggregation.
4. Allow dissolution to proceed for 5–10 minutes at room temperature. Gently swirl if needed. A clear, colorless solution should result.
5. Inspect for visible particulates — if present, discard and reconstitute a fresh vial.

Storage of Reconstituted Solutions

Reconstituted oxytocin is more susceptible to degradation than the lyophilized form due to disulfide bond vulnerability in solution:

• Immediate aliquoting is essential. Divide into single-use aliquots to eliminate the need for repeated freeze-thaw cycles.
• Refrigerated storage (2–8°C): Suitable for short-term storage of reconstituted solutions. Use promptly.
• Frozen storage (-20°C or -80°C): Preferred for keeping single-use aliquots longer. Colder storage is generally used for longer periods.
• Avoid: Repeated freeze-thaw cycles (maximum: one freeze-thaw per aliquot). Discard unused thawed aliquots — do not refreeze.

Stability Considerations

Oxytocin degradation pathways in research settings include:

• Disulfide bond reduction/scrambling: Primary degradation route. Prevent by maintaining reducing-agent-free conditions and using deoxygenated buffers where practical.
• Deamidation: The Asn⁵ residue is susceptible to deamidation under alkaline conditions, producing aspartic acid and isoaspartate variants with altered biological activity.
• Oxidation: The Tyr² residue can undergo oxidation to dityrosine under prolonged exposure to light and oxygen.
• Adsorption: Oxytocin can adsorb to glass and plastic surfaces at low concentrations (<10 μg/mL). Siliconized or low-protein-binding containers are recommended for low-concentration solutions.

Quality Control Recommendations

• RP-HPLC: Expected purity 99%+. Monitor for degradation peaks (reduced oxytocin, deamidated variants).
• Mass spectrometry: Confirms the molecular identity of intact cyclic oxytocin. Where a Certificate of Analysis is published on our COA page, refer to it for identity and mass results.
• Ellman’s assay (DTNB): Detects free thiols indicative of disulfide reduction. Intact oxytocin should show negligible free thiol content.
• Functional assay: For critical experiments, verify biological activity via OXTR-expressing cell line calcium flux assay.

Research Design Considerations

Published oxytocin research highlights several variables that laboratories commonly control for when designing and interpreting experiments with this research peptide. This information is research context only. Research-grade material is not manufactured or certified for human or veterinary use.

• Vasopressin receptor cross-reactivity: At higher concentrations, oxytocin also binds vasopressin V_1a and V₂ receptors. Receptor-selective controls help attribute observed signaling to OXTR.
• Tissue-specific OXTR expression: OXTR is expressed in uterine and mammary smooth muscle, vascular endothelium, kidney and brain. Assay results depend on the receptor density of the model used.
• Sex and hormonal status: Published findings in behavioral models often differ by sex, gonadal steroid status and individual OXTR expression, so sex-balanced designs are common.
• Context dependence: Behavioral findings in animal models depend on social context, prior experience and the brain region studied, which is why careful controls and pre-registered endpoints are recommended.
• Institutional approval: All animal work should follow protocols approved by the relevant institutional animal care and use committee (IACUC).

Laboratory Safety

Standard laboratory safety protocols: wear appropriate PPE (gloves, lab coat, eye protection), handle in a biosafety cabinet, avoid aerosol generation from lyophilized powder, and dispose of unused material per institutional guidelines. In case of skin or eye contact, flush with copious water for 15 minutes. Oxytocin is not classified as acutely toxic, but appropriate laboratory hygiene — including hand washing and prohibition of eating/drinking in the work area — must be maintained.

Oxytocin 5mg FAQ

What is Oxytocin 5mg?

Oxytocin 5mg is a vial containing 5 mg of lyophilized oxytocin, a cyclic nine-amino-acid peptide (CAS 50-56-6, C43H66N12O12S2, approx. 1007.2 g/mol) with a disulfide bridge between its two cysteine residues. It is used in neuroendocrine, social-behavior and oxytocin-receptor research. For protocols that need more material, the same peptide is available as Oxytocin 10mg.

Is the Oxytocin 5mg from BioSim Peptides third-party tested?

Yes. Oxytocin 5mg is supplied at 99%+ purity and is third-party tested by an independent laboratory. Certificates of analysis are published on our COA page rather than shipped in the package. If a certificate for the current lot is not listed yet, contact us before you order.

How should Oxytocin 5mg be stored?

Lyophilized Oxytocin is generally stored at -20°C, protected from light and moisture. After reconstitution, published handling guidance is to keep the solution at 2-8°C, split it into aliquots and avoid repeated freeze-thaw cycles. Avoid reducing agents, which can break the peptide’s disulfide bond. Our peptide storage and stability guide covers handling in more detail.

How fast does BioSim Peptides ship?

Orders ship in 2 business days. Delivery time depends on your location and the shipping method selected at checkout.

Is Oxytocin 5mg from BioSim Peptides intended for human use?

No. Oxytocin 5mg is supplied for laboratory research use only and is not for human consumption. It is not a drug, dietary supplement, cosmetic, or food, and is not intended for diagnosis, treatment, cure, or prevention of any disease in humans or animals.

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