Peptide Basics
Neuropeptides: What They Are, Examples and How They Differ From Neurotransmitters
Neuropeptides are peptides that nerve cells release to carry signals to other cells. They include the endorphins and enkephalins, substance P, neuropeptide Y, the orexins and vasopressin. This page sets out the definition the U.S. National Library of Medicine uses, sixteen neuropeptides, from two amino acids (carnosine) to 41 (CRH), with their lengths checked in UniProt, how one precursor yields several of them, how they differ from classical neurotransmitters such as glutamate, and where they overlap with hormones and medicines.
What makes a peptide a neuropeptide
MeSH defines neuropeptides as peptides released by neurons as intercellular messengers, and adds that many of them are also hormones released by non-neuronal cells. A 2011 review by J.P. Burbach puts it more narrowly: small proteinaceous substances produced and released by neurons through the regulated secretory route and acting on neural substrates. By that definition, the review counts almost 70 genes in the mammalian genome that encode neuropeptide precursors. The chemistry is the same as any other peptide, a short chain of amino acids (see what peptides are); what makes it a neuropeptide is the cell that releases it.
MeSH files 34 headings under neuropeptides. Several are whole families: the opioid peptides (enkephalins, dynorphins and endorphins, each from its own precursor), the tachykinins (substance P and the neurokinins, which share a conserved ending, Phe-X-Gly-Leu-Met-NH2), the orexins, the melanocyte-stimulating hormones and the hypothalamic hormones. Others are single molecules such as neuropeptide Y, galanin, neurotensin and calcitonin gene-related peptide.
Neuropeptide examples, shortest to longest
Every length below is the human sequence as UniProt records it, or the MeSH description where no single gene applies (carnosine, DSIP); the group is the MeSH heading the peptide sits under.
| Neuropeptide | MeSH group | Amino acids | Note |
|---|---|---|---|
| Carnosine | Neuropeptides (own heading) | 2 | MeSH calls it a naturally occurring dipeptide neuropeptide. |
| Met-enkephalin and Leu-enkephalin | Opioid peptides › enkephalins | 5 | One precursor, proenkephalin, holds four copies of Met-enkephalin and one of Leu-enkephalin. |
| Vasopressin | Vasopressins | 9 | Made in the hypothalamus with its carrier protein, neurophysin 2. |
| Delta sleep-inducing peptide (DSIP) | Neuropeptides (own heading) | 9 | A nonapeptide found in neurons, peripheral organs and plasma. |
| Kisspeptin-10 | Kisspeptins | 10 | The last ten amino acids of the 54-residue kisspeptin. |
| Substance P | Tachykinins | 11 | Cut from the same precursor as neurokinin A (10); both end in methionine amide. |
| Alpha-MSH | Melanocyte-stimulating hormones | 13 | Cut from POMC, the precursor that also gives ACTH and beta-endorphin. |
| Neurotensin | Neuropeptides (own heading) | 13 | First isolated from the hypothalamus. |
| Dynorphin A | Opioid peptides › dynorphins | 17 | From prodynorphin, which also holds three Leu-enkephalin sequences. |
| Vasoactive intestinal peptide (VIP) | Neuropeptides (own heading) | 28 | Ends in asparagine amide. |
| Orexin-B and orexin-A | Orexins | 28 and 33 | Both cut from one precursor, hypocretin; orexin-A has two disulfide bonds. |
| Galanin | Neuropeptides (own heading) | 30 | 30 in humans; MeSH notes 29 or 30 depending on the species. |
| Beta-endorphin | Opioid peptides › endorphins | 31 | The last 31 amino acids of POMC. |
| Neuropeptide Y (NPY) | Neuropeptides (own heading) | 36 | Ends in tyrosine amide; present in many sympathetic noradrenergic neurons. |
| Calcitonin gene-related peptide (CGRP) | Neuropeptides (own heading) | 37 | Made from the calcitonin gene by alternative processing of its mRNA. |
| Corticotropin-releasing hormone (CRH) | Hypothalamic hormones | 41 | Made by neurons of the paraventricular nucleus; ends in isoleucine amide. |
Sources: UniProt P01210, P01185, Q15726, P20366, P01189, P30990, P01213, P01282, O43612, P22466, P01303, P06881 and P06850; NLM MeSH descriptors D009479, D002336, D018847, D004745, D014667, D003701, D059648, D015320, D013373, D009074, D009496, D014660, D000068797, D019004, D009478, D015740, D007028 and D003346. Read 28 October 2026.
How neurons make them: one precursor, several peptides
Like peptide hormones, neuropeptides are made from a gene as part of a longer precursor protein, which the cell cuts into the active peptides. UniProt’s records show how much one precursor can hold:
- Proenkephalin (267 amino acids) carries four copies of Met-enkephalin and one of Leu-enkephalin, plus longer extended forms.
- Prodynorphin yields dynorphin A (17), the neoendorphins and three Leu-enkephalin sequences.
- POMC yields alpha-MSH (13), ACTH (39) and beta-endorphin (31), so one precursor feeds both the opioid and melanocortin families.
- Protachykinin-1 yields substance P (11) and neurokinin A (10).
- The hypocretin precursor yields orexin-A (33) and orexin-B (28).
- The calcitonin gene gives calcitonin and, by alternative processing of its mRNA, CGRP (37), which MeSH describes as widely distributed in the brain, gut and perivascular nerves.
Many are finished with an amide at the end of the chain, which UniProt records as a modified residue: methionine amide on substance P and neurokinin A, tyrosine amide on neuropeptide Y, phenylalanine amide on CGRP, isoleucine amide on CRH, asparagine amide on VIP. The tachykinins share a conserved ending, Phe-X-Gly-Leu-Met-NH2 (X varies), which MeSH uses to define the family.
Sources: UniProt P01210, P01213, P01189, P20366, O43612, P06881, P01303, P06850 and P01282; MeSH D015320 and D015740. Read 28 October 2026.
Neuropeptides vs classical neurotransmitters
Nerve cells signal with two kinds of messenger, and the same circuits use both. The fast ones are small molecules such as glutamate and GABA; neuropeptides are slower and act as modulators, adjusting how strongly a circuit responds.
| Neuropeptide | Classical neurotransmitter | |
|---|---|---|
| What it is | A chain of amino acids cut from a precursor protein | A small molecule such as glutamate or GABA |
| Where it is stored | Dense core vesicles | Clear synaptic vesicles |
| What triggers release | Usually high-frequency firing; single action potentials are not enough | A single action potential |
| Where it acts | Can diffuse some distance from the release site | Mainly at the synapse |
| How fast it acts | Slow; acts through G-protein-coupled receptors | Fast |
Distribution differs too. A 2012 review notes that some neuropeptides, such as orexin, are made in only one region of the brain, while others, such as neuropeptide Y, are made throughout it by neurons with no connection to one another.
Sources: Tallent, Results Probl Cell Differ 2008 (PMID 17554500); van den Pol, Neuron 2012 (PMID 23040809); Burbach, Methods Mol Biol 2011 (PMID 21922398). Read 28 October 2026.
Neuropeptides, hormones and medicines
The line between a neuropeptide and a peptide hormone is the route, not the molecule. Vasopressin is made by neurons in the hypothalamus and released into the blood from the posterior pituitary; CRH is made by neurons of the paraventricular nucleus and carried to the pituitary in its portal circulation; VIP is released by neurons and from the intestinal mucosa. MeSH files the hypothalamic hormones, CRH among them, under both neuropeptides and peptide hormones.
Several approved medicines are copies or analogues of neuropeptides, or act on their receptors. Their U.S. labels say:
| Medicine | Neuropeptide system | What the label says |
|---|---|---|
| Oxytocin (Pitocin) | Oxytocin | Synthetic oxytocin; the label calls it a nonapeptide. |
| Desmopressin | Vasopressin | A synthetic analogue of 8-arginine vasopressin, the antidiuretic hormone. |
| Bremelanotide (Vyleesi) | Melanocortins (the alpha-MSH family) | A melanocortin receptor agonist; the label describes a synthetic cyclic heptapeptide (7). |
Sources: MeSH D007028, D003346, D014660, D009496 and D009479; U.S. labels via openFDA for Pitocin (6 May 2026), desmopressin acetate tablets (13 November 2025) and Vyleesi (13 November 2025). Read 28 October 2026.
Where research compounds fit
Several research peptides are neuropeptides or are built on one. DSIP has its own MeSH heading under neuropeptides; oxytocin and VIP are the natural molecules; kisspeptin-10 is the last ten amino acids of kisspeptin; Semax is filed in MeSH as the ACTH 4-7 fragment extended by Pro-Gly-Pro; melanotan II is filed in MeSH as a cyclic analogue of alpha-MSH; and PT-141 (bremelanotide) is a cyclic heptapeptide that acts on melanocortin receptors. Each guide sets out the compound’s identity, research history and regulatory status.
Medibact does not manufacture or sell peptides. We supply USP-grade bacteriostatic water, made in the USA, for research use only, and publish reference material like this page.
Where this sits in the rest of the reference
FAQ
What are neuropeptides?
Neuropeptides are peptides that nerve cells release to signal to other cells. The U.S. National Library of Medicine’s MeSH vocabulary defines them as peptides released by neurons as intercellular messengers, and notes that many are also hormones released by non-neuronal cells. Even a dipeptide qualifies: MeSH files carnosine, two amino acids long, as a neuropeptide, while corticotropin-releasing hormone has 41.
What are examples of neuropeptides?
The opioid peptides (enkephalins, dynorphins and beta-endorphin), substance P and the other tachykinins, neuropeptide Y, the orexins, calcitonin gene-related peptide (CGRP), galanin, neurotensin, vasoactive intestinal peptide (VIP), vasopressin, kisspeptin, alpha-MSH and the hypothalamic releasing hormones such as CRH. MeSH lists 34 headings under neuropeptides.
What is the difference between a neuropeptide and a neurotransmitter?
Classical neurotransmitters such as glutamate and GABA are small molecules stored in clear synaptic vesicles and released by a single nerve impulse at the synapse. Neuropeptides are amino-acid chains stored in dense core vesicles, usually released only during high-frequency firing, and they can diffuse some distance to act on G-protein-coupled receptors, so their effects are slower and modulating. The terms overlap: MeSH itself calls substance P a neurotransmitter.
How many neuropeptides are there?
There is no single fixed count. A 2011 review by J.P. Burbach counted almost 70 genes in the mammalian genome that encode neuropeptide precursors, and each precursor can be cut into several active peptides. MeSH files 34 narrower headings under neuropeptides, several of which are whole families.
Are neuropeptides hormones?
Some are both. MeSH notes that many neuropeptides are also hormones released by non-neuronal cells. Vasopressin and CRH are made by neurons in the hypothalamus and act as hormones; VIP is released by neurons and from the intestinal mucosa. The difference is the route: a hormone travels in the blood, while a neuropeptide acts from a nerve cell on nearby cells.
How are neuropeptides made?
From a gene, as part of a longer precursor protein that is cut into the active peptides. UniProt records show how much one precursor can hold: proenkephalin carries four copies of Met-enkephalin and one of Leu-enkephalin, protachykinin gives substance P and neurokinin A, and the hypocretin precursor gives both orexins. Many are finished with an amide at the end of the chain.
Is neuropeptide Y a neuropeptide or a hormone?
A neuropeptide. Neuropeptide Y is a 36-amino-acid peptide that MeSH describes as present in many organs and in many sympathetic noradrenergic neurons, and it is filed under neuropeptides in its own right. A 2012 review notes that it is made throughout the brain.
Are any medicines based on neuropeptides?
Yes. U.S. labels describe oxytocin injection as synthetic oxytocin, desmopressin as a synthetic analogue of vasopressin, and bremelanotide as a synthetic cyclic heptapeptide that acts on melanocortin receptors.
Is this medical advice?
No. This page explains what neuropeptides are, from public scientific and regulatory sources. It gives no dose, protocol or recommendation, and peptides sold for research are labelled research use only, not for human use. Medibact supplies USP-grade bacteriostatic water, made in the USA, and is not affiliated with any manufacturer of the products named here.
References: NLM MeSH descriptors D009479, D018847, D004745, D015320, D013373, D009478, D000068797, D015740, D019004, D009496, D003701, D059648, D009074, D014660, D009481, D002336, D007028 and D003346, and supplementary records C048487 and C079282; UniProt P20366, P01210, P01213, P01189, P01185, Q15726, P30990, O43612, P01282, P22466, P01303, P06881 and P06850; PubMed 21922398, 17554500 and 23040809; U.S. labels for Pitocin, desmopressin acetate and Vyleesi via openFDA. Read 28 October 2026.
Educational use only — not medical advice. This guide summarizes information reported in published research and community practice for educational purposes. It is not medical advice and not a recommendation to use any compound. Any doses, schedules, or combinations shown are examples of what has been reported, not instructions for you. Many peptides described here are research compounds that are not FDA-approved for the uses discussed and may be investigational or restricted. Effects, risks, and legal status vary; individual needs and results vary. Consult a qualified, licensed healthcare professional before making any decision. Do not use this content to diagnose, treat, or dose yourself.