Galanin: natural nerve-calming peptide (porcine form)
A natural signaling peptide found throughout the brain and spinal cord that calms overactive nerve cells, helping to reduce nerve pain and seizures; used as a lab research tool.
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
Galanin is a 29-amino-acid neuropeptide first isolated from pig small intestine, and it is one of the most widely distributed peptides in the mammalian nervous system. It was discovered because of its unusual chemistry — the researchers were specifically hunting for peptides with a C-terminal amide cap, and galanin turned up in the screen (Tatemoto 1983). The stored sequence GWTLNSAGYLLGPHAIDNHRSFHDKYGLA does not show the amide group on the final alanine, but the amide is part of the natural molecule and is what the receptor recognizes. The peptide acts on a family of three G-protein-coupled receptors (GalR1, GalR2, GalR3) that are expressed broadly across brain, spinal cord, gut, and endocrine tissues (Webling 2012).
History
Tatemoto and colleagues at the Karolinska Institute isolated galanin from porcine intestinal extracts in 1983, using a chemical detection method that targeted C-terminally amidated peptides — a strategy that had previously turned up other novel neuropeptides. The original report named the peptide "galanin" from its N-terminal galycine and C-terminal alaninamide, gave the full 29-residue sequence, and noted its ability to contract smooth muscle preparations and to produce a mild, sustained hyperglycemia in dogs (Tatemoto 1983). Over the next two decades, three distinct galanin receptors were cloned: GalR1, then GalR2 (Wang 1997), and finally GalR3 (Smith 1998). A related peptide, galanin-like peptide (GALP), was later identified as a hypothalamic regulator of energy balance and reproduction (Lawrence 2011).
What it does
Galanin is mostly an inhibitory neuropeptide. When it engages its receptors on a neuron, the typical net effect is to dampen that neuron's firing rate and to reduce neurotransmitter release at its synapses. This inhibitory profile underpins the two effects that draw the most therapeutic interest: protection of brain neurons from injury, and modulation of pain and seizure thresholds. Galanin expression rises sharply in many brain regions after nerve injury and is elevated in the basal forebrain of patients with Alzheimer's disease (Elliott-Hunt 2007), which has long been interpreted as a compensatory protective response.
The peptide also has peripheral actions consistent with its gut origin: in the original isolation work it contracted smooth muscle preparations and produced a mild, sustained hyperglycemia in dogs (Tatemoto 1983). GALP, the related family member, sits in the hypothalamus and influences feeding and reproductive signaling (Lawrence 2011).
Mechanism
Galanin signals through three G-protein-coupled receptors. GalR1 and GalR3 couple predominantly to inhibitory Gi/o pathways, while GalR2 couples to multiple G-protein families and can engage both inhibitory and excitatory downstream effectors (Webling 2012, Gopalakrishnan 2021). The three receptors have distinct but overlapping tissue distributions, which is why the same peptide can produce different effects depending on which neurons and which receptor subtypes are expressed locally.
Genetic and pharmacological dissection has clarified which subtype does what. In hippocampal cultures, the neuroprotective action of galanin is lost in animals carrying a loss-of-function mutation in GalR2, indicating that GalR2 is the subtype that mediates galanin's protection of hippocampal neurons from damage (Elliott-Hunt 2007). Cloning and expression work mapped the binding pharmacology and second-messenger coupling of each receptor as they were identified (Wang 1997, Smith 1998), and more recent network-level analyses have assembled the full set of known galanin–receptor signaling interactions into an integrated pathway map (Gopalakrishnan 2021).
Evidence
- Human: No human clinical trials of galanin itself are documented in the dossier. Galanin expression is elevated in the basal forebrain of patients with Alzheimer's disease (Elliott-Hunt 2007), and galanin receptors have been proposed as a therapeutic target for neurological disease (Freimann 2015), but receptor-directed drug development has not produced an approved galanin-pathway therapeutic to date based on the available sources.
- Animal: Loss-of-function studies in mice show that GalR2 mediates galanin's protective effect on hippocampal neurons (Elliott-Hunt 2007). In dogs, exogenous galanin produces a mild, sustained hyperglycemia (Tatemoto 1983).
- In vitro: The original isolation work demonstrated galanin's ability to contract rat smooth muscle preparations (Tatemoto 1983). Cloning studies established ligand binding and signal transduction profiles for each of the three galanin receptor subtypes in heterologous expression systems (Wang 1997, Smith 1998).
Known effects
- Neuroprotection (hippocampus) — Preclinical; GalR2-mediated (Elliott-Hunt 2007).
- Modulation of neuronal excitability — Preclinical / mechanistic; broadly inhibitory effect on neuronal firing across multiple brain regions (Webling 2012).
- Hyperglycemia — Demonstrated in dogs in the original isolation report (Tatemoto 1983).
- Smooth-muscle contraction — Demonstrated in rat smooth-muscle preparations (Tatemoto 1983).
- Hypothalamic regulation of energy balance and reproduction — Attributed to the related family peptide GALP (Lawrence 2011).
Regulatory status
No approved drug product based on galanin itself or its receptors is documented in the available sources. Galanin receptors have been reviewed as a potential therapeutic target for neurological disease, but no approval status has been established (Freimann 2015).
Open questions
- Which galanin receptor subtype to target for which indication remains an open translational question — GalR1, GalR2, and GalR3 have overlapping but distinct distributions, and the available reviews argue that subtype-selective ligands are the key bottleneck (Webling 2012, Freimann 2015).
- The mapped galanin signaling network is now reasonably complete at the receptor and second-messenger level (Gopalakrishnan 2021), but how that network produces the divergent effects observed across brain regions in vivo is not fully resolved by the dossier sources.
- No human clinical trial data on galanin or galanin-receptor ligands is captured in this dossier.
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.
Could a tiny dose of a natural brain-protecting molecule be safer for long-term use than a larger dose?
If this holds, it would mean that at very low doses the peptide activates only one protective pathway, avoiding a second pathway linked to cell overgrowth and cancer risk. For people taking a galanin-based drug long-term, for Alzheimer's disease or epilepsy, that distinction could matter a great deal for safety.
Is there a way to stop life-threatening seizures when the usual drugs have stopped working?
Benzodiazepine-refractory status epilepticus, a prolonged seizure emergency that stops responding to standard treatment, carries a 20 to 30 percent death rate and has few rescue options. If this hypothesis holds, a galanin-based drug could stop the seizure through a completely separate mechanism, giving doctors a tool they currently lack.
Could scientists build a much smaller, drug-like version of a therapeutic peptide by copying just its most important piece?
The full 29-amino-acid galanin peptide is too large and fragile to become a practical drug for the brain. If one residue, tryptophan at position 2, turns out to carry most of the binding power, chemists could design a compact mimetic built around that anchor. That smaller molecule would be far more likely to reach the brain and become a real medicine for conditions like Alzheimer's disease or epilepsy.
Is there a natural brake in the brain that could slow down early puberty or hormone-sensitive cancers, and could a drug target it?
Current treatments for early puberty and hormone-sensitive cancers like certain breast and prostate cancers work by blocking hormones further down the chain. If this hypothesis holds, a drug targeting a brain receptor called GalR3 could suppress the whole hormonal cascade earlier and through a different mechanism, potentially offering a new option where existing therapies fall short or cause side effects.
Could decades of research using pig galanin have given us a slightly skewed picture of how the human version works?
Much foundational research on galanin used the porcine peptide because it was isolated first. If the pig and human versions bind two of the three galanin receptors at different relative strengths, then studies of pain, memory, and Alzheimer's disease that relied on the porcine peptide as a stand-in may need to be reinterpreted before those findings can guide human drug development.
▸full evidence table2 metrics
| metric | value | tool |
|---|---|---|
| ipTM | 0.8242278099060059 | boltz-2 |
| ranking score | 0.7720207571983337 | 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{pep10563,
sequence = {GWTLNSAGYLLGPHAIDNHRSFHDKYGLA},
target = {galr1},
author = {peptidemodel},
year = {2026},
status = {synthesized}
}