Vasotocin: natural bonding and contraction hormone found in fish and other animals
A small hormone from non-mammalian animals (fish, frogs, birds, reptiles) that drives womb contractions, water balance, and social bonding; used only as a lab research tool.
- Class
- Neurohypophysial neuropeptide (fish-derived)
- Status
- No approved therapeutic status identified
- Main caveat
- No functional bioactivity, animal efficacy, or human evidence is attached to this card. Sequence and gene-expression context from grass puffer only.
A researcher, an agent, or an algorithm wrote down the sequence and picked a target to hit.
An AI model like OpenFold3 or AlphaFold built a 3D structure and scored how well it fits the binding site.
A second contributor repeated the computation on their own hardware and the scores matched.
A chemistry service or a researcher ordered the sequence, it was manufactured, and mass spectrometry confirmed the right molecule was produced.
A binding or activity measurement confirmed that it actually does what the computer predicted — or didn't.
What this is
Vasotocin (also called arginine vasotocin, or AVT) is a nine-residue neurohypophysial hormone found throughout non-mammalian vertebrates — fish, amphibians, reptiles, and birds — where it serves roles broadly equivalent to both oxytocin and vasopressin in mammals. It acts primarily at the oxytocin receptor (OXTR), a class A G-protein-coupled receptor, and drives a range of effects including smooth-muscle contraction, water balance, and social behavior. The sequence stored here, CYIQNCPR, is the eight-residue backbone; the natural peptide is nine residues (CYIQNCPRG with a C-terminal glycinamide) and carries a disulfide bridge between the cysteines at positions 1 and 6 that is essential for its three-dimensional ring structure and receptor binding — neither the terminal glycinamide nor the disulfide bond is encoded in the raw stored sequence (Möller and colleagues, 2007; Motohashi and colleagues, 2008).
History
Vasotocin was characterized across a wide range of non-mammalian vertebrate species long before the molecular era. Motohashi and colleagues (2008) cloned and sequenced the neurohypophysial hormone genes — including the vasotocin gene — from the grass puffer Takifugu niphobles, documenting its gene structure and seasonal changes in expression during the spawning period. The same study situated vasotocin within the broader classification of neurohypophysial hormones: vertebrate species typically carry one vasopressin-like peptide and one oxytocin-like peptide, and in non-mammalian vertebrates vasotocin occupies the vasopressin-like slot. Möller and colleagues (2007), in work characterizing a related conopressin from cone snail venom, provided a cross-species alignment confirming that CYIQNCPRG is the canonical vasotocin sequence found in non-mammalian vertebrates.
What it does
Vasotocin acts at oxytocin and vasopressin receptors to regulate two broad domains: reproductive physiology and social behavior. On the physiological side, it stimulates smooth-muscle contraction in the uterus and related tissues, and plays roles in water and ion balance in aquatic species. Motohashi and colleagues (2008) documented that vasotocin gene expression in the grass puffer changes markedly across the spawning season, consistent with a reproductive coordination role. On the behavioral side, vasotocin has been shown to modulate social and sexual behavior across a broad range of vertebrate species, with effects including pair-bond formation, aggression, and communication (Motohashi and colleagues, 2008).
Evidence
- Human: No human clinical trials have been conducted with this peptide.
- Animal: Vasotocin's behavioral and reproductive effects have been characterized in fish, amphibians, and other non-mammalian vertebrates. Motohashi and colleagues (2008) documented gene expression changes in grass puffer across the spawning season. Vasotocin has been identified biochemically in species including cartilaginous fishes and amphibians, confirmed through chromatographic and pharmacological methods.
- In vitro: Vasotocin binds both vasopressin-type and oxytocin-type receptors. The Möller and colleagues (2007) cross-species alignment places it within the vasopressin/oxytocin superfamily alongside conopressins, diuretic hormones, and related neuropeptides, all sharing the conserved disulfide-bridged nonapeptide scaffold.
Known effects
- Smooth-muscle contraction (uterotonic) — Preclinical; well established in non-mammalian vertebrate models
- Social and sexual behavior modulation — Preclinical; documented across fish, amphibian, and reptile species (Motohashi and colleagues, 2008)
- Water and ion balance — Preclinical; vasopressin-like osmoregulatory role in aquatic vertebrates
- Spawning coordination — Preclinical; gene expression changes during reproductive season in grass puffer (Motohashi and colleagues, 2008)
Regulatory status
- US: Not approved by the FDA. No IND or NDA on record. Research-use status.
- EU: Not approved by the EMA.
- WADA: No specific listing; would fall under general peptide hormone provisions if used in sport contexts.
Related peptides
Vasotocin belongs to the neurohypophysial nonapeptide superfamily. Its closest mammalian counterparts are oxytocin and vasopressin (arginine vasopressin), which arose from a common ancestral gene. Related platform cards include oxytocin, the mammalian oxytocin-receptor agonist that shares the same core ring structure and C-terminal amide, and vasopressin (arginine vasopressin), the mammalian vasopressin-family counterpart. Möller and colleagues (2007) described conopressins — venom-derived vasotocin/oxytocin-related peptides from cone snails — as a further branch of the same superfamily.
Research directions for this peptide, selected from the current sources — hypotheses you can explore and model. None of it is proven yet; tap any one to see the full thinking.
Does vasotocin trigger only some of the oxytocin receptor's effects, potentially leaving out the ones that cause side effects?
If vasotocin preferentially activates brain-based bonding pathways without triggering uterine contractions, it could become the basis for safer social-behavior medicines, particularly important for pregnant women or people with cardiovascular sensitivities.
Could chemists use vasotocin's ring structure as a scaffold to build a tougher, more durable hormone-mimicking medicine?
Hormone peptide drugs are quickly broken down in the body. If vasotocin's compact ring can be locked into a double-constrained shape, it could become a stable pill or injection that treats conditions like uterine dysfunction or social disorders without needing repeated dosing.
Could a hormone from fish and birds work better than human oxytocin in the brain to help people with social difficulties?
If true, people with autism spectrum disorder or social anxiety might benefit from a new class of medicines that activates the bonding receptor differently, especially if current oxytocin-based treatments continue to show inconsistent results.
Does swapping one building block between vasotocin and oxytocin change how tightly the peptide grips its receptor?
If R8 is a key binding booster, chemists could add it to synthetic oxytocin-like drugs to make them stick to the receptor longer, potentially needing lower doses with fewer side effects.
▸full evidence table2 metrics
| metric | value | tool |
|---|---|---|
| ipTM | 0.9835274815559387 | boltz-2 |
| ranking score | 0.8751110434532166 | boltz-2 |
▸3-letter notation
▸recipeboltz-2 2.2.1
| parameter | value |
|---|---|
| model | boltz-2 2.2.1 |
| weights | — |
| hardware | vast_v100_32gb |
| mlx version | — |
| python | — |
| random seed | 1 |
| msa strategy | colabfold_local |
| runtime | — |
| predicted by | — |
| predicted at | 2026-05-22 |
▸citationbibtex
@peptide{pep10516,
sequence = {CYIQNCPR},
target = {oxtr},
author = {peptidemodel},
year = {2026},
status = {synthesized}
}